media/extractors/mp3/MP3Extractor.cpp - LeafOS-Project/android_frameworks_av - Gitiles

 /*
  * Copyright (C) 2009 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 //#define LOG_NDEBUG 0
 #define LOG_TAG "MP3Extractor"
 #include <utils/Log.h>

 #include "MP3Extractor.h"

 #include "ID3.h"
 #include "VBRISeeker.h"
 #include "XINGSeeker.h"

 #include <media/stagefright/foundation/ADebug.h>
 #include <media/stagefright/foundation/AMessage.h>
 #include <media/stagefright/foundation/avc_utils.h>
 #include <media/stagefright/foundation/ByteUtils.h>
 #include <media/stagefright/MediaBufferBase.h>
 #include <media/stagefright/MediaBufferGroup.h>
 #include <media/stagefright/MediaDefs.h>
 #include <media/stagefright/MediaErrors.h>
 #include <media/stagefright/MetaData.h>
 #include <utils/String8.h>

 namespace android {

 // Everything must match except for
 // protection, bitrate, padding, private bits, mode, mode extension,
 // copyright bit, original bit and emphasis.
 // Yes ... there are things that must indeed match...
 static const uint32_t kMask = 0xfffe0c00;

 static bool Resync(
         DataSourceHelper *source, uint32_t match_header,
         off64_t *inout_pos, off64_t *post_id3_pos, uint32_t *out_header) {
     if (post_id3_pos != NULL) {
         *post_id3_pos = 0;
     }

     if (*inout_pos == 0) {
         // Skip an optional ID3 header if syncing at the very beginning
         // of the datasource.

         for (;;) {
             uint8_t id3header[10];
             if (source->readAt(*inout_pos, id3header, sizeof(id3header))
                     < (ssize_t)sizeof(id3header)) {
                 // If we can't even read these 10 bytes, we might as well bail
                 // out, even if there _were_ 10 bytes of valid mp3 audio data...
                 return false;
             }

             if (memcmp("ID3", id3header, 3)) {
                 break;
             }

             // Skip the ID3v2 header.

             size_t len =
                 ((id3header[6] & 0x7f) << 21)
                 | ((id3header[7] & 0x7f) << 14)
                 | ((id3header[8] & 0x7f) << 7)
                 | (id3header[9] & 0x7f);

             len += 10;

             *inout_pos += len;

             ALOGV("skipped ID3 tag, new starting offset is %lld (0x%016llx)",
                     (long long)*inout_pos, (long long)*inout_pos);
         }

         if (post_id3_pos != NULL) {
             *post_id3_pos = *inout_pos;
         }
     }

     off64_t pos = *inout_pos;
     bool valid = false;

     const size_t kMaxReadBytes = 1024;
     const size_t kMaxBytesChecked = 128 * 1024;
     uint8_t buf[kMaxReadBytes];
     ssize_t bytesToRead = kMaxReadBytes;
     ssize_t totalBytesRead = 0;
     ssize_t remainingBytes = 0;
     bool reachEOS = false;
     uint8_t *tmp = buf;

     do {
         if (pos >= (off64_t)(*inout_pos + kMaxBytesChecked)) {
             // Don't scan forever.
             ALOGV("giving up at offset %lld", (long long)pos);
             break;
         }

         if (remainingBytes < 4) {
             if (reachEOS) {
                 break;
             } else {
                 memcpy(buf, tmp, remainingBytes);
                 bytesToRead = kMaxReadBytes - remainingBytes;

                 /*
                  * The next read position should start from the end of
                  * the last buffer, and thus should include the remaining
                  * bytes in the buffer.
                  */
                 totalBytesRead = source->readAt(pos + remainingBytes,
                                                 buf + remainingBytes,
                                                 bytesToRead);
                 if (totalBytesRead <= 0) {
                     break;
                 }
                 reachEOS = (totalBytesRead != bytesToRead);
                 totalBytesRead += remainingBytes;
                 remainingBytes = totalBytesRead;
                 tmp = buf;
                 continue;
             }
         }

         uint32_t header = U32_AT(tmp);

         if (match_header != 0 && (header & kMask) != (match_header & kMask)) {
             ++pos;
             ++tmp;
             --remainingBytes;
             continue;
         }

         size_t frame_size;
         int sample_rate, num_channels, bitrate;
         if (!GetMPEGAudioFrameSize(
                     header, &frame_size,
                     &sample_rate, &num_channels, &bitrate)) {
             ++pos;
             ++tmp;
             --remainingBytes;
             continue;
         }

         ALOGV("found possible 1st frame at %lld (header = 0x%08x)", (long long)pos, header);

         // We found what looks like a valid frame,
         // now find its successors.

         off64_t test_pos = pos + frame_size;

         valid = true;
         for (int j = 0; j < 3; ++j) {
             uint8_t tmp[4];
             if (source->readAt(test_pos, tmp, 4) < 4) {
                 valid = false;
                 break;
             }

             uint32_t test_header = U32_AT(tmp);

             ALOGV("subsequent header is %08x", test_header);

             if ((test_header & kMask) != (header & kMask)) {
                 valid = false;
                 break;
             }

             size_t test_frame_size;
             if (!GetMPEGAudioFrameSize(
                         test_header, &test_frame_size)) {
                 valid = false;
                 break;
             }

             ALOGV("found subsequent frame #%d at %lld", j + 2, (long long)test_pos);

             test_pos += test_frame_size;
         }

         if (valid) {
             *inout_pos = pos;

             if (out_header != NULL) {
                 *out_header = header;
             }
         } else {
             ALOGV("no dice, no valid sequence of frames found.");
         }

         ++pos;
         ++tmp;
         --remainingBytes;
     } while (!valid);

     return valid;
 }

 class MP3Source : public MediaTrackHelper {
 public:
     MP3Source(
             AMediaFormat *meta, DataSourceHelper *source,
             off64_t first_frame_pos, uint32_t fixed_header,
             MP3Seeker *seeker);

     virtual media_status_t start();
     virtual media_status_t stop();

     virtual media_status_t getFormat(AMediaFormat *meta);

     virtual media_status_t read(
             MediaBufferHelper **buffer, const ReadOptions *options = NULL);

 protected:
     virtual ~MP3Source();

 private:
     static const size_t kMaxFrameSize;
     AMediaFormat *mMeta = NULL;
     DataSourceHelper *mDataSource = NULL;
     off64_t mFirstFramePos = 0;
     uint32_t mFixedHeader = 0;
     off64_t mCurrentPos = 0;
     int64_t mCurrentTimeUs = 0;
     bool mStarted = false;
     MP3Seeker *mSeeker = NULL;

     int64_t mBasisTimeUs = 0;
     int64_t mSamplesRead = 0;

     MP3Source(const MP3Source &);
     MP3Source &operator=(const MP3Source &);
 };

 struct Mp3Meta {
     off64_t pos;
     off64_t post_id3_pos;
     uint32_t header;
 };

 MP3Extractor::MP3Extractor(
         DataSourceHelper *source, Mp3Meta *meta)
     : mDataSource(source) {

     off64_t pos = 0;
     off64_t post_id3_pos;
     uint32_t header;
     bool success;

     if (meta != NULL) {
         // The sniffer has already done all the hard work for us, simply
         // accept its judgement.
         pos = meta->pos;
         header = meta->header;
         post_id3_pos = meta->post_id3_pos;
         success = true;
     } else {
         success = Resync(mDataSource, 0, &pos, &post_id3_pos, &header);
     }

     if (!success) {
         // mInitCheck will remain NO_INIT
         return;
     }

     mFirstFramePos = pos;
     mFixedHeader = header;
     XINGSeeker *seeker = XINGSeeker::CreateFromSource(mDataSource, mFirstFramePos);

     mMeta = AMediaFormat_new();
     if (seeker == NULL) {
         mSeeker = VBRISeeker::CreateFromSource(mDataSource, post_id3_pos);
     } else {
         mSeeker = seeker;
         int encd = seeker->getEncoderDelay();
         int encp = seeker->getEncoderPadding();
         if (encd != 0 || encp != 0) {
             AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_DELAY, encd);
             AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_PADDING, encp);
         }
     }

     if (mSeeker != NULL) {
         // While it is safe to send the XING/VBRI frame to the decoder, this will
         // result in an extra 1152 samples being output. In addition, the bitrate
         // of the Xing header might not match the rest of the file, which could
         // lead to problems when seeking. The real first frame to decode is after
         // the XING/VBRI frame, so skip there.
         size_t frame_size;
         int sample_rate;
         int num_channels;
         int bitrate;
         GetMPEGAudioFrameSize(
                 header, &frame_size, &sample_rate, &num_channels, &bitrate);
         pos += frame_size;
         if (!Resync(mDataSource, 0, &pos, &post_id3_pos, &header)) {
             // mInitCheck will remain NO_INIT
             return;
         }
         mFirstFramePos = pos;
         mFixedHeader = header;
     }

     size_t frame_size;
     int sample_rate;
     int num_channels;
     int bitrate;
     GetMPEGAudioFrameSize(
             header, &frame_size, &sample_rate, &num_channels, &bitrate);

     unsigned layer = 4 - ((header >> 17) & 3);

     switch (layer) {
         case 1:
             AMediaFormat_setString(mMeta,
                     AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG_LAYER_I);
             break;
         case 2:
             AMediaFormat_setString(mMeta,
                     AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG_LAYER_II);
             break;
         case 3:
             AMediaFormat_setString(mMeta, AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG);
             break;
         default:
             TRESPASS();
     }

     AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_SAMPLE_RATE, sample_rate);
     AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_BIT_RATE, bitrate * 1000);
     AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_CHANNEL_COUNT, num_channels);

     int64_t durationUs;

     if (mSeeker == NULL || !mSeeker->getDuration(&durationUs)) {
         off64_t fileSize;
         if (mDataSource->getSize(&fileSize) == OK) {
             off64_t dataLength = fileSize - mFirstFramePos;
             if (dataLength > INT64_MAX / 8000LL) {
                 // duration would overflow
                 durationUs = INT64_MAX;
             } else {
                 durationUs = 8000LL * dataLength / bitrate;
             }
         } else {
             durationUs = -1;
         }
     }

     if (durationUs >= 0) {
         AMediaFormat_setInt64(mMeta, AMEDIAFORMAT_KEY_DURATION, durationUs);
     }

     mInitCheck = OK;

     // Get iTunes-style gapless info if present.
     // When getting the id3 tag, skip the V1 tags to prevent the source cache
     // from being iterated to the end of the file.
     DataSourceHelper helper(mDataSource);
     ID3 id3(&helper, true);
     if (id3.isValid()) {
         ID3::Iterator *com = new ID3::Iterator(id3, "COM");
         if (com->done()) {
             delete com;
             com = new ID3::Iterator(id3, "COMM");
         }
         while(!com->done()) {
             String8 commentdesc;
             String8 commentvalue;
             com->getString(&commentdesc, &commentvalue);
             const char * desc = commentdesc.string();
             const char * value = commentvalue.string();

             // first 3 characters are the language, which we don't care about
             if(strlen(desc) > 3 && strcmp(desc + 3, "iTunSMPB") == 0) {

                 int32_t delay, padding;
                 if (sscanf(value, " %*x %x %x %*x", &delay, &padding) == 2) {
                     AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_DELAY, delay);
                     AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_PADDING, padding);
                 }
                 break;
             }
             com->next();
         }
         delete com;
         com = NULL;
     }
 }

 MP3Extractor::~MP3Extractor() {
     delete mSeeker;
     delete mDataSource;
     AMediaFormat_delete(mMeta);
 }

 size_t MP3Extractor::countTracks() {
     return mInitCheck != OK ? 0 : 1;
 }

 MediaTrackHelper *MP3Extractor::getTrack(size_t index) {
     if (mInitCheck != OK || index != 0) {
         return NULL;
     }

     return new MP3Source(
             mMeta, mDataSource, mFirstFramePos, mFixedHeader,
             mSeeker);
 }

 media_status_t MP3Extractor::getTrackMetaData(
         AMediaFormat *meta,
         size_t index, uint32_t /* flags */) {
     if (mInitCheck != OK || index != 0) {
         return AMEDIA_ERROR_UNKNOWN;
     }
     return AMediaFormat_copy(meta, mMeta);
 }

 ////////////////////////////////////////////////////////////////////////////////

 // The theoretical maximum frame size for an MPEG audio stream should occur
 // while playing a Layer 2, MPEGv2.5 audio stream at 160kbps (with padding).
 // The size of this frame should be...
 // ((1152 samples/frame * 160000 bits/sec) /
 //  (8000 samples/sec * 8 bits/byte)) + 1 padding byte/frame = 2881 bytes/frame.
 // Set our max frame size to the nearest power of 2 above this size (aka, 4kB)
 const size_t MP3Source::kMaxFrameSize = (1 << 12); /* 4096 bytes */

 MP3Source::MP3Source(
         AMediaFormat *meta, DataSourceHelper *source,
         off64_t first_frame_pos, uint32_t fixed_header,
         MP3Seeker *seeker)
     : mMeta(meta),
       mDataSource(source),
       mFirstFramePos(first_frame_pos),
       mFixedHeader(fixed_header),
       mSeeker(seeker) {
 }

 MP3Source::~MP3Source() {
     if (mStarted) {
         stop();
     }
 }

 media_status_t MP3Source::start() {
     CHECK(!mStarted);

     mBufferGroup->add_buffer(kMaxFrameSize);

     mCurrentPos = mFirstFramePos;
     mCurrentTimeUs = 0;

     mBasisTimeUs = mCurrentTimeUs;
     mSamplesRead = 0;

     mStarted = true;

     return AMEDIA_OK;
 }

 media_status_t MP3Source::stop() {
     CHECK(mStarted);

     mStarted = false;

     return AMEDIA_OK;
 }

 media_status_t MP3Source::getFormat(AMediaFormat *meta) {
     return AMediaFormat_copy(meta, mMeta);
 }

 media_status_t MP3Source::read(
         MediaBufferHelper **out, const ReadOptions *options) {
     *out = NULL;

     int64_t seekTimeUs;
     ReadOptions::SeekMode mode;
     bool seekCBR = false;

     if (options != NULL && options->getSeekTo(&seekTimeUs, &mode)) {
         int64_t actualSeekTimeUs = seekTimeUs;
         if (mSeeker == NULL
                 || !mSeeker->getOffsetForTime(&actualSeekTimeUs, &mCurrentPos)) {
             int32_t bitrate;
             if (!AMediaFormat_getInt32(mMeta, AMEDIAFORMAT_KEY_BIT_RATE, &bitrate)) {
                 // bitrate is in bits/sec.
                 ALOGI("no bitrate");

                 return AMEDIA_ERROR_UNSUPPORTED;
             }

             mCurrentTimeUs = seekTimeUs;
             mCurrentPos = mFirstFramePos + seekTimeUs * bitrate / 8000000;
             seekCBR = true;
         } else {
             mCurrentTimeUs = actualSeekTimeUs;
         }

         mBasisTimeUs = mCurrentTimeUs;
         mSamplesRead = 0;
     }

     MediaBufferHelper *buffer;
     status_t err = mBufferGroup->acquire_buffer(&buffer);
     if (err != OK) {
         return AMEDIA_ERROR_UNKNOWN;
     }

     size_t frame_size;
     int bitrate;
     int num_samples;
     int sample_rate;
     for (;;) {
         ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), 4);
         if (n < 4) {
             buffer->release();
             buffer = NULL;

             return ((n < 0 && n != ERROR_END_OF_STREAM) ?
                     AMEDIA_ERROR_UNKNOWN : AMEDIA_ERROR_END_OF_STREAM);
         }

         uint32_t header = U32_AT((const uint8_t *)buffer->data());

         if ((header & kMask) == (mFixedHeader & kMask)
             && GetMPEGAudioFrameSize(
                 header, &frame_size, &sample_rate, NULL,
                 &bitrate, &num_samples)) {

             // re-calculate mCurrentTimeUs because we might have called Resync()
             if (seekCBR) {
                 mCurrentTimeUs = (mCurrentPos - mFirstFramePos) * 8000 / bitrate;
                 mBasisTimeUs = mCurrentTimeUs;
             }

             break;
         }

         // Lost sync.
         ALOGV("lost sync! header = 0x%08x, old header = 0x%08x\n", header, mFixedHeader);

         off64_t pos = mCurrentPos;
         if (!Resync(mDataSource, mFixedHeader, &pos, NULL, NULL)) {
             ALOGE("Unable to resync. Signalling end of stream.");

             buffer->release();
             buffer = NULL;

             return AMEDIA_ERROR_END_OF_STREAM;
         }

         mCurrentPos = pos;

         // Try again with the new position.
     }

     CHECK(frame_size <= buffer->size());

     ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), frame_size);
     if (n < (ssize_t)frame_size) {
         buffer->release();
         buffer = NULL;

         return ((n < 0 && n != ERROR_END_OF_STREAM) ?
                 AMEDIA_ERROR_UNKNOWN : AMEDIA_ERROR_END_OF_STREAM);
     }

     buffer->set_range(0, frame_size);

     AMediaFormat *meta = buffer->meta_data();
     AMediaFormat_setInt64(meta, AMEDIAFORMAT_KEY_TIME_US, mCurrentTimeUs);
     AMediaFormat_setInt32(meta, AMEDIAFORMAT_KEY_IS_SYNC_FRAME, 1);

     mCurrentPos += frame_size;

     mSamplesRead += num_samples;
     mCurrentTimeUs = mBasisTimeUs + ((mSamplesRead * 1000000) / sample_rate);

     *out = buffer;

     return AMEDIA_OK;
 }

 media_status_t MP3Extractor::getMetaData(AMediaFormat *meta) {
     AMediaFormat_clear(meta);
     if (mInitCheck != OK) {
         return AMEDIA_ERROR_UNKNOWN;
     }
     AMediaFormat_setString(meta, AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG);

     DataSourceHelper helper(mDataSource);
     ID3 id3(&helper);

     if (!id3.isValid()) {
         return AMEDIA_OK;
     }

     struct Map {
         const char *key;
         const char *tag1;
         const char *tag2;
     };
     static const Map kMap[] = {
         { AMEDIAFORMAT_KEY_ALBUM, "TALB", "TAL" },
         { AMEDIAFORMAT_KEY_ARTIST, "TPE1", "TP1" },
         { AMEDIAFORMAT_KEY_ALBUMARTIST, "TPE2", "TP2" },
         { AMEDIAFORMAT_KEY_COMPOSER, "TCOM", "TCM" },
         { AMEDIAFORMAT_KEY_GENRE, "TCON", "TCO" },
         { AMEDIAFORMAT_KEY_TITLE, "TIT2", "TT2" },
         { AMEDIAFORMAT_KEY_YEAR, "TYE", "TYER" },
         { AMEDIAFORMAT_KEY_AUTHOR, "TXT", "TEXT" },
         { AMEDIAFORMAT_KEY_CDTRACKNUMBER, "TRK", "TRCK" },
         { AMEDIAFORMAT_KEY_DISCNUMBER, "TPA", "TPOS" },
         { AMEDIAFORMAT_KEY_COMPILATION, "TCP", "TCMP" },
     };
     static const size_t kNumMapEntries = sizeof(kMap) / sizeof(kMap[0]);

     for (size_t i = 0; i < kNumMapEntries; ++i) {
         ID3::Iterator *it = new ID3::Iterator(id3, kMap[i].tag1);
         if (it->done()) {
             delete it;
             it = new ID3::Iterator(id3, kMap[i].tag2);
         }

         if (it->done()) {
             delete it;
             continue;
         }

         String8 s;
         it->getString(&s);
         delete it;

         AMediaFormat_setString(meta, kMap[i].key, s.string());
     }

     size_t dataSize;
     String8 mime;
     const void *data = id3.getAlbumArt(&dataSize, &mime);

     if (data) {
         AMediaFormat_setBuffer(meta, AMEDIAFORMAT_KEY_ALBUMART, data, dataSize);
     }

     return AMEDIA_OK;
 }

 static CMediaExtractor* CreateExtractor(
         CDataSource *source,
         void *meta) {
     Mp3Meta *metaData = static_cast<Mp3Meta *>(meta);
     return wrap(new MP3Extractor(new DataSourceHelper(source), metaData));
 }

 static CreatorFunc Sniff(
         CDataSource *source, float *confidence, void **meta,
         FreeMetaFunc *freeMeta) {
     off64_t pos = 0;
     off64_t post_id3_pos;
     uint32_t header;
     uint8_t mpeg_header[5];
     DataSourceHelper helper(source);
     if (helper.readAt(0, mpeg_header, sizeof(mpeg_header)) < (ssize_t)sizeof(mpeg_header)) {
         return NULL;
     }

     if (!memcmp("\x00\x00\x01\xba", mpeg_header, 4) && (mpeg_header[4] >> 4) == 2) {
         ALOGV("MPEG1PS container is not supported!");
         return NULL;
     }
     if (!Resync(&helper, 0, &pos, &post_id3_pos, &header)) {
         return NULL;
     }

     Mp3Meta *mp3Meta = new Mp3Meta;
     mp3Meta->pos = pos;
     mp3Meta->header = header;
     mp3Meta->post_id3_pos = post_id3_pos;
     *meta = mp3Meta;
     *freeMeta = ::free;

     *confidence = 0.2f;

     return CreateExtractor;
 }

 static const char *extensions[] = {
     "mp2",
     "mp3",
     "mpeg",
     "mpg",
     "mpga",
     NULL
 };

 extern "C" {
 // This is the only symbol that needs to be exported
 __attribute__ ((visibility ("default")))
 ExtractorDef GETEXTRACTORDEF() {
     return {
         EXTRACTORDEF_VERSION,
         UUID("812a3f6c-c8cf-46de-b529-3774b14103d4"),
         1, // version
         "MP3 Extractor",
         { .v3 = {Sniff, extensions} }
     };
 }

 } // extern "C"

 }  // namespace android
	/*
	* Copyright (C) 2009 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	//#define LOG_NDEBUG 0
	#define LOG_TAG "MP3Extractor"
	#include <utils/Log.h>

	#include "MP3Extractor.h"

	#include "ID3.h"
	#include "VBRISeeker.h"
	#include "XINGSeeker.h"

	#include <media/stagefright/foundation/ADebug.h>
	#include <media/stagefright/foundation/AMessage.h>
	#include <media/stagefright/foundation/avc_utils.h>
	#include <media/stagefright/foundation/ByteUtils.h>
	#include <media/stagefright/MediaBufferBase.h>
	#include <media/stagefright/MediaBufferGroup.h>
	#include <media/stagefright/MediaDefs.h>
	#include <media/stagefright/MediaErrors.h>
	#include <media/stagefright/MetaData.h>
	#include <utils/String8.h>

	namespace android {

	// Everything must match except for
	// protection, bitrate, padding, private bits, mode, mode extension,
	// copyright bit, original bit and emphasis.
	// Yes ... there are things that must indeed match...
	static const uint32_t kMask = 0xfffe0c00;

	static bool Resync(
	DataSourceHelper *source, uint32_t match_header,
	off64_t inout_pos, off64_t post_id3_pos, uint32_t *out_header) {
	if (post_id3_pos != NULL) {
	*post_id3_pos = 0;
	}

	if (*inout_pos == 0) {
	// Skip an optional ID3 header if syncing at the very beginning
	// of the datasource.

	for (;;) {
	uint8_t id3header[10];
	if (source->readAt(*inout_pos, id3header, sizeof(id3header))
	< (ssize_t)sizeof(id3header)) {
	// If we can't even read these 10 bytes, we might as well bail
	// out, even if there _were_ 10 bytes of valid mp3 audio data...
	return false;
	}

	if (memcmp("ID3", id3header, 3)) {
	break;
	}

	// Skip the ID3v2 header.

	size_t len =
	((id3header[6] & 0x7f) << 21)
	\| ((id3header[7] & 0x7f) << 14)
	\| ((id3header[8] & 0x7f) << 7)
	\| (id3header[9] & 0x7f);

	len += 10;

	*inout_pos += len;

	ALOGV("skipped ID3 tag, new starting offset is %lld (0x%016llx)",
	(long long)inout_pos, (long long)inout_pos);
	}

	if (post_id3_pos != NULL) {
	post_id3_pos = inout_pos;
	}
	}

	off64_t pos = *inout_pos;
	bool valid = false;

	const size_t kMaxReadBytes = 1024;
	const size_t kMaxBytesChecked = 128 * 1024;
	uint8_t buf[kMaxReadBytes];
	ssize_t bytesToRead = kMaxReadBytes;
	ssize_t totalBytesRead = 0;
	ssize_t remainingBytes = 0;
	bool reachEOS = false;
	uint8_t *tmp = buf;

	do {
	if (pos >= (off64_t)(*inout_pos + kMaxBytesChecked)) {
	// Don't scan forever.
	ALOGV("giving up at offset %lld", (long long)pos);
	break;
	}

	if (remainingBytes < 4) {
	if (reachEOS) {
	break;
	} else {
	memcpy(buf, tmp, remainingBytes);
	bytesToRead = kMaxReadBytes - remainingBytes;

	/*
	* The next read position should start from the end of
	* the last buffer, and thus should include the remaining
	* bytes in the buffer.
	*/
	totalBytesRead = source->readAt(pos + remainingBytes,
	buf + remainingBytes,
	bytesToRead);
	if (totalBytesRead <= 0) {
	break;
	}
	reachEOS = (totalBytesRead != bytesToRead);
	totalBytesRead += remainingBytes;
	remainingBytes = totalBytesRead;
	tmp = buf;
	continue;
	}
	}

	uint32_t header = U32_AT(tmp);

	if (match_header != 0 && (header & kMask) != (match_header & kMask)) {
	++pos;
	++tmp;
	--remainingBytes;
	continue;
	}

	size_t frame_size;
	int sample_rate, num_channels, bitrate;
	if (!GetMPEGAudioFrameSize(
	header, &frame_size,
	&sample_rate, &num_channels, &bitrate)) {
	++pos;
	++tmp;
	--remainingBytes;
	continue;
	}

	ALOGV("found possible 1st frame at %lld (header = 0x%08x)", (long long)pos, header);

	// We found what looks like a valid frame,
	// now find its successors.

	off64_t test_pos = pos + frame_size;

	valid = true;
	for (int j = 0; j < 3; ++j) {
	uint8_t tmp[4];
	if (source->readAt(test_pos, tmp, 4) < 4) {
	valid = false;
	break;
	}

	uint32_t test_header = U32_AT(tmp);

	ALOGV("subsequent header is %08x", test_header);

	if ((test_header & kMask) != (header & kMask)) {
	valid = false;
	break;
	}

	size_t test_frame_size;
	if (!GetMPEGAudioFrameSize(
	test_header, &test_frame_size)) {
	valid = false;
	break;
	}

	ALOGV("found subsequent frame #%d at %lld", j + 2, (long long)test_pos);

	test_pos += test_frame_size;
	}

	if (valid) {
	*inout_pos = pos;

	if (out_header != NULL) {
	*out_header = header;
	}
	} else {
	ALOGV("no dice, no valid sequence of frames found.");
	}

	++pos;
	++tmp;
	--remainingBytes;
	} while (!valid);

	return valid;
	}

	class MP3Source : public MediaTrackHelper {
	public:
	MP3Source(
	AMediaFormat meta, DataSourceHelper source,
	off64_t first_frame_pos, uint32_t fixed_header,
	MP3Seeker *seeker);

	virtual media_status_t start();
	virtual media_status_t stop();

	virtual media_status_t getFormat(AMediaFormat *meta);

	virtual media_status_t read(
	MediaBufferHelper *buffer, const ReadOptions options = NULL);

	protected:
	virtual ~MP3Source();

	private:
	static const size_t kMaxFrameSize;
	AMediaFormat *mMeta = NULL;
	DataSourceHelper *mDataSource = NULL;
	off64_t mFirstFramePos = 0;
	uint32_t mFixedHeader = 0;
	off64_t mCurrentPos = 0;
	int64_t mCurrentTimeUs = 0;
	bool mStarted = false;
	MP3Seeker *mSeeker = NULL;

	int64_t mBasisTimeUs = 0;
	int64_t mSamplesRead = 0;

	MP3Source(const MP3Source &);
	MP3Source &operator=(const MP3Source &);
	};

	struct Mp3Meta {
	off64_t pos;
	off64_t post_id3_pos;
	uint32_t header;
	};

	MP3Extractor::MP3Extractor(
	DataSourceHelper source, Mp3Meta meta)
	: mDataSource(source) {

	off64_t pos = 0;
	off64_t post_id3_pos;
	uint32_t header;
	bool success;

	if (meta != NULL) {
	// The sniffer has already done all the hard work for us, simply
	// accept its judgement.
	pos = meta->pos;
	header = meta->header;
	post_id3_pos = meta->post_id3_pos;
	success = true;
	} else {
	success = Resync(mDataSource, 0, &pos, &post_id3_pos, &header);
	}

	if (!success) {
	// mInitCheck will remain NO_INIT
	return;
	}

	mFirstFramePos = pos;
	mFixedHeader = header;
	XINGSeeker *seeker = XINGSeeker::CreateFromSource(mDataSource, mFirstFramePos);

	mMeta = AMediaFormat_new();
	if (seeker == NULL) {
	mSeeker = VBRISeeker::CreateFromSource(mDataSource, post_id3_pos);
	} else {
	mSeeker = seeker;
	int encd = seeker->getEncoderDelay();
	int encp = seeker->getEncoderPadding();
	if (encd != 0 \|\| encp != 0) {
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_DELAY, encd);
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_PADDING, encp);
	}
	}

	if (mSeeker != NULL) {
	// While it is safe to send the XING/VBRI frame to the decoder, this will
	// result in an extra 1152 samples being output. In addition, the bitrate
	// of the Xing header might not match the rest of the file, which could
	// lead to problems when seeking. The real first frame to decode is after
	// the XING/VBRI frame, so skip there.
	size_t frame_size;
	int sample_rate;
	int num_channels;
	int bitrate;
	GetMPEGAudioFrameSize(
	header, &frame_size, &sample_rate, &num_channels, &bitrate);
	pos += frame_size;
	if (!Resync(mDataSource, 0, &pos, &post_id3_pos, &header)) {
	// mInitCheck will remain NO_INIT
	return;
	}
	mFirstFramePos = pos;
	mFixedHeader = header;
	}

	size_t frame_size;
	int sample_rate;
	int num_channels;
	int bitrate;
	GetMPEGAudioFrameSize(
	header, &frame_size, &sample_rate, &num_channels, &bitrate);

	unsigned layer = 4 - ((header >> 17) & 3);

	switch (layer) {
	case 1:
	AMediaFormat_setString(mMeta,
	AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG_LAYER_I);
	break;
	case 2:
	AMediaFormat_setString(mMeta,
	AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG_LAYER_II);
	break;
	case 3:
	AMediaFormat_setString(mMeta, AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG);
	break;
	default:
	TRESPASS();
	}

	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_SAMPLE_RATE, sample_rate);
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_BIT_RATE, bitrate * 1000);
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_CHANNEL_COUNT, num_channels);

	int64_t durationUs;

	if (mSeeker == NULL \|\| !mSeeker->getDuration(&durationUs)) {
	off64_t fileSize;
	if (mDataSource->getSize(&fileSize) == OK) {
	off64_t dataLength = fileSize - mFirstFramePos;
	if (dataLength > INT64_MAX / 8000LL) {
	// duration would overflow
	durationUs = INT64_MAX;
	} else {
	durationUs = 8000LL * dataLength / bitrate;
	}
	} else {
	durationUs = -1;
	}
	}

	if (durationUs >= 0) {
	AMediaFormat_setInt64(mMeta, AMEDIAFORMAT_KEY_DURATION, durationUs);
	}

	mInitCheck = OK;

	// Get iTunes-style gapless info if present.
	// When getting the id3 tag, skip the V1 tags to prevent the source cache
	// from being iterated to the end of the file.
	DataSourceHelper helper(mDataSource);
	ID3 id3(&helper, true);
	if (id3.isValid()) {
	ID3::Iterator *com = new ID3::Iterator(id3, "COM");
	if (com->done()) {
	delete com;
	com = new ID3::Iterator(id3, "COMM");
	}
	while(!com->done()) {
	String8 commentdesc;
	String8 commentvalue;
	com->getString(&commentdesc, &commentvalue);
	const char * desc = commentdesc.string();
	const char * value = commentvalue.string();

	// first 3 characters are the language, which we don't care about
	if(strlen(desc) > 3 && strcmp(desc + 3, "iTunSMPB") == 0) {

	int32_t delay, padding;
	if (sscanf(value, " %x %x %x %x", &delay, &padding) == 2) {
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_DELAY, delay);
	AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_ENCODER_PADDING, padding);
	}
	break;
	}
	com->next();
	}
	delete com;
	com = NULL;
	}
	}

	MP3Extractor::~MP3Extractor() {
	delete mSeeker;
	delete mDataSource;
	AMediaFormat_delete(mMeta);
	}

	size_t MP3Extractor::countTracks() {
	return mInitCheck != OK ? 0 : 1;
	}

	MediaTrackHelper *MP3Extractor::getTrack(size_t index) {
	if (mInitCheck != OK \|\| index != 0) {
	return NULL;
	}

	return new MP3Source(
	mMeta, mDataSource, mFirstFramePos, mFixedHeader,
	mSeeker);
	}

	media_status_t MP3Extractor::getTrackMetaData(
	AMediaFormat *meta,
	size_t index, uint32_t /* flags */) {
	if (mInitCheck != OK \|\| index != 0) {
	return AMEDIA_ERROR_UNKNOWN;
	}
	return AMediaFormat_copy(meta, mMeta);
	}

	////////////////////////////////////////////////////////////////////////////////

	// The theoretical maximum frame size for an MPEG audio stream should occur
	// while playing a Layer 2, MPEGv2.5 audio stream at 160kbps (with padding).
	// The size of this frame should be...
	// ((1152 samples/frame * 160000 bits/sec) /
	// (8000 samples/sec * 8 bits/byte)) + 1 padding byte/frame = 2881 bytes/frame.
	// Set our max frame size to the nearest power of 2 above this size (aka, 4kB)
	const size_t MP3Source::kMaxFrameSize = (1 << 12); /* 4096 bytes */

	MP3Source::MP3Source(
	AMediaFormat meta, DataSourceHelper source,
	off64_t first_frame_pos, uint32_t fixed_header,
	MP3Seeker *seeker)
	: mMeta(meta),
	mDataSource(source),
	mFirstFramePos(first_frame_pos),
	mFixedHeader(fixed_header),
	mSeeker(seeker) {
	}

	MP3Source::~MP3Source() {
	if (mStarted) {
	stop();
	}
	}

	media_status_t MP3Source::start() {
	CHECK(!mStarted);

	mBufferGroup->add_buffer(kMaxFrameSize);

	mCurrentPos = mFirstFramePos;
	mCurrentTimeUs = 0;

	mBasisTimeUs = mCurrentTimeUs;
	mSamplesRead = 0;

	mStarted = true;

	return AMEDIA_OK;
	}

	media_status_t MP3Source::stop() {
	CHECK(mStarted);

	mStarted = false;

	return AMEDIA_OK;
	}

	media_status_t MP3Source::getFormat(AMediaFormat *meta) {
	return AMediaFormat_copy(meta, mMeta);
	}

	media_status_t MP3Source::read(
	MediaBufferHelper *out, const ReadOptions options) {
	*out = NULL;

	int64_t seekTimeUs;
	ReadOptions::SeekMode mode;
	bool seekCBR = false;

	if (options != NULL && options->getSeekTo(&seekTimeUs, &mode)) {
	int64_t actualSeekTimeUs = seekTimeUs;
	if (mSeeker == NULL
	\|\| !mSeeker->getOffsetForTime(&actualSeekTimeUs, &mCurrentPos)) {
	int32_t bitrate;
	if (!AMediaFormat_getInt32(mMeta, AMEDIAFORMAT_KEY_BIT_RATE, &bitrate)) {
	// bitrate is in bits/sec.
	ALOGI("no bitrate");

	return AMEDIA_ERROR_UNSUPPORTED;
	}

	mCurrentTimeUs = seekTimeUs;
	mCurrentPos = mFirstFramePos + seekTimeUs * bitrate / 8000000;
	seekCBR = true;
	} else {
	mCurrentTimeUs = actualSeekTimeUs;
	}

	mBasisTimeUs = mCurrentTimeUs;
	mSamplesRead = 0;
	}

	MediaBufferHelper *buffer;
	status_t err = mBufferGroup->acquire_buffer(&buffer);
	if (err != OK) {
	return AMEDIA_ERROR_UNKNOWN;
	}

	size_t frame_size;
	int bitrate;
	int num_samples;
	int sample_rate;
	for (;;) {
	ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), 4);
	if (n < 4) {
	buffer->release();
	buffer = NULL;

	return ((n < 0 && n != ERROR_END_OF_STREAM) ?
	AMEDIA_ERROR_UNKNOWN : AMEDIA_ERROR_END_OF_STREAM);
	}

	uint32_t header = U32_AT((const uint8_t *)buffer->data());

	if ((header & kMask) == (mFixedHeader & kMask)
	&& GetMPEGAudioFrameSize(
	header, &frame_size, &sample_rate, NULL,
	&bitrate, &num_samples)) {

	// re-calculate mCurrentTimeUs because we might have called Resync()
	if (seekCBR) {
	mCurrentTimeUs = (mCurrentPos - mFirstFramePos) * 8000 / bitrate;
	mBasisTimeUs = mCurrentTimeUs;
	}

	break;
	}

	// Lost sync.
	ALOGV("lost sync! header = 0x%08x, old header = 0x%08x\n", header, mFixedHeader);

	off64_t pos = mCurrentPos;
	if (!Resync(mDataSource, mFixedHeader, &pos, NULL, NULL)) {
	ALOGE("Unable to resync. Signalling end of stream.");

	buffer->release();
	buffer = NULL;

	return AMEDIA_ERROR_END_OF_STREAM;
	}

	mCurrentPos = pos;

	// Try again with the new position.
	}

	CHECK(frame_size <= buffer->size());

	ssize_t n = mDataSource->readAt(mCurrentPos, buffer->data(), frame_size);
	if (n < (ssize_t)frame_size) {
	buffer->release();
	buffer = NULL;

	return ((n < 0 && n != ERROR_END_OF_STREAM) ?
	AMEDIA_ERROR_UNKNOWN : AMEDIA_ERROR_END_OF_STREAM);
	}

	buffer->set_range(0, frame_size);

	AMediaFormat *meta = buffer->meta_data();
	AMediaFormat_setInt64(meta, AMEDIAFORMAT_KEY_TIME_US, mCurrentTimeUs);
	AMediaFormat_setInt32(meta, AMEDIAFORMAT_KEY_IS_SYNC_FRAME, 1);

	mCurrentPos += frame_size;

	mSamplesRead += num_samples;
	mCurrentTimeUs = mBasisTimeUs + ((mSamplesRead * 1000000) / sample_rate);

	*out = buffer;

	return AMEDIA_OK;
	}

	media_status_t MP3Extractor::getMetaData(AMediaFormat *meta) {
	AMediaFormat_clear(meta);
	if (mInitCheck != OK) {
	return AMEDIA_ERROR_UNKNOWN;
	}
	AMediaFormat_setString(meta, AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_MPEG);

	DataSourceHelper helper(mDataSource);
	ID3 id3(&helper);

	if (!id3.isValid()) {
	return AMEDIA_OK;
	}

	struct Map {
	const char *key;
	const char *tag1;
	const char *tag2;
	};
	static const Map kMap[] = {
	{ AMEDIAFORMAT_KEY_ALBUM, "TALB", "TAL" },
	{ AMEDIAFORMAT_KEY_ARTIST, "TPE1", "TP1" },
	{ AMEDIAFORMAT_KEY_ALBUMARTIST, "TPE2", "TP2" },
	{ AMEDIAFORMAT_KEY_COMPOSER, "TCOM", "TCM" },
	{ AMEDIAFORMAT_KEY_GENRE, "TCON", "TCO" },
	{ AMEDIAFORMAT_KEY_TITLE, "TIT2", "TT2" },
	{ AMEDIAFORMAT_KEY_YEAR, "TYE", "TYER" },
	{ AMEDIAFORMAT_KEY_AUTHOR, "TXT", "TEXT" },
	{ AMEDIAFORMAT_KEY_CDTRACKNUMBER, "TRK", "TRCK" },
	{ AMEDIAFORMAT_KEY_DISCNUMBER, "TPA", "TPOS" },
	{ AMEDIAFORMAT_KEY_COMPILATION, "TCP", "TCMP" },
	};
	static const size_t kNumMapEntries = sizeof(kMap) / sizeof(kMap[0]);

	for (size_t i = 0; i < kNumMapEntries; ++i) {
	ID3::Iterator *it = new ID3::Iterator(id3, kMap[i].tag1);
	if (it->done()) {
	delete it;
	it = new ID3::Iterator(id3, kMap[i].tag2);
	}

	if (it->done()) {
	delete it;
	continue;
	}

	String8 s;
	it->getString(&s);
	delete it;

	AMediaFormat_setString(meta, kMap[i].key, s.string());
	}

	size_t dataSize;
	String8 mime;
	const void *data = id3.getAlbumArt(&dataSize, &mime);

	if (data) {
	AMediaFormat_setBuffer(meta, AMEDIAFORMAT_KEY_ALBUMART, data, dataSize);
	}

	return AMEDIA_OK;
	}

	static CMediaExtractor* CreateExtractor(
	CDataSource *source,
	void *meta) {
	Mp3Meta metaData = static_cast<Mp3Meta >(meta);
	return wrap(new MP3Extractor(new DataSourceHelper(source), metaData));
	}

	static CreatorFunc Sniff(
	CDataSource source, float confidence, void **meta,
	FreeMetaFunc *freeMeta) {
	off64_t pos = 0;
	off64_t post_id3_pos;
	uint32_t header;
	uint8_t mpeg_header[5];
	DataSourceHelper helper(source);
	if (helper.readAt(0, mpeg_header, sizeof(mpeg_header)) < (ssize_t)sizeof(mpeg_header)) {
	return NULL;
	}

	if (!memcmp("\x00\x00\x01\xba", mpeg_header, 4) && (mpeg_header[4] >> 4) == 2) {
	ALOGV("MPEG1PS container is not supported!");
	return NULL;
	}
	if (!Resync(&helper, 0, &pos, &post_id3_pos, &header)) {
	return NULL;
	}

	Mp3Meta *mp3Meta = new Mp3Meta;
	mp3Meta->pos = pos;
	mp3Meta->header = header;
	mp3Meta->post_id3_pos = post_id3_pos;
	*meta = mp3Meta;
	*freeMeta = ::free;

	*confidence = 0.2f;

	return CreateExtractor;
	}

	static const char *extensions[] = {
	"mp2",
	"mp3",
	"mpeg",
	"mpg",
	"mpga",
	NULL
	};

	extern "C" {
	// This is the only symbol that needs to be exported
	__attribute__ ((visibility ("default")))
	ExtractorDef GETEXTRACTORDEF() {
	return {
	EXTRACTORDEF_VERSION,
	UUID("812a3f6c-c8cf-46de-b529-3774b14103d4"),
	1, // version
	"MP3 Extractor",
	{ .v3 = {Sniff, extensions} }
	};
	}

	} // extern "C"

	} // namespace android