media/extractors/aac/AACExtractor.cpp

/*
 * Copyright (C) 2011 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 "AACExtractor"
#include <utils/Log.h>

#include "AACExtractor.h"
#include <media/MediaExtractorPluginApi.h>
#include <media/stagefright/foundation/ABuffer.h>
#include <media/stagefright/foundation/AMessage.h>
#include <media/stagefright/foundation/ADebug.h>
#include <media/stagefright/MediaBufferGroup.h>
#include <media/stagefright/MediaDefs.h>
#include <media/stagefright/MediaErrors.h>
#include <media/stagefright/MetaDataUtils.h>
#include <utils/String8.h>

namespace android {

class AACSource : public MediaTrackHelper {
public:
    AACSource(
            DataSourceHelper *source,
            AMediaFormat *meta,
            const Vector<uint64_t> &offset_vector,
            int64_t frame_duration_us);

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

    virtual media_status_t getFormat(AMediaFormat*);

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

protected:
    virtual ~AACSource();

private:
    static const size_t kMaxFrameSize;
    DataSourceHelper *mDataSource;
    AMediaFormat *mMeta;

    off64_t mOffset;
    int64_t mCurrentTimeUs;
    bool mStarted;

    Vector<uint64_t> mOffsetVector;
    int64_t mFrameDurationUs;

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

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

// Returns the sample rate based on the sampling frequency index
uint32_t get_sample_rate(const uint8_t sf_index)
{
    static const uint32_t sample_rates[] =
    {
        96000, 88200, 64000, 48000, 44100, 32000,
        24000, 22050, 16000, 12000, 11025, 8000
    };

    if (sf_index < sizeof(sample_rates) / sizeof(sample_rates[0])) {
        return sample_rates[sf_index];
    }

    return 0;
}

// Returns the frame length in bytes as described in an ADTS header starting at the given offset,
//     or 0 if the size can't be read due to an error in the header or a read failure.
// The returned value is the AAC frame size with the ADTS header length (regardless of
//     the presence of the CRC).
// If headerSize is non-NULL, it will be used to return the size of the header of this ADTS frame.
static size_t getAdtsFrameLength(DataSourceHelper *source, off64_t offset, size_t* headerSize) {

    const size_t kAdtsHeaderLengthNoCrc = 7;
    const size_t kAdtsHeaderLengthWithCrc = 9;

    size_t frameSize = 0;

    uint8_t syncword[2];
    if (source->readAt(offset, &syncword, 2) != 2) {
        return 0;
    }
    if ((syncword[0] != 0xff) || ((syncword[1] & 0xf6) != 0xf0)) {
        return 0;
    }

    uint8_t protectionAbsent;
    if (source->readAt(offset + 1, &protectionAbsent, 1) < 1) {
        return 0;
    }
    protectionAbsent &= 0x1;

    uint8_t header[3];
    if (source->readAt(offset + 3, &header, 3) < 3) {
        return 0;
    }

    frameSize = (header[0] & 0x3) << 11 | header[1] << 3 | header[2] >> 5;

    // protectionAbsent is 0 if there is CRC
    size_t headSize = protectionAbsent ? kAdtsHeaderLengthNoCrc : kAdtsHeaderLengthWithCrc;
    if (headSize > frameSize) {
        return 0;
    }
    if (headerSize != NULL) {
        *headerSize = headSize;
    }

    return frameSize;
}

AACExtractor::AACExtractor(
        DataSourceHelper *source, off64_t offset)
    : mDataSource(source),
      mInitCheck(NO_INIT),
      mFrameDurationUs(0) {

    uint8_t profile, sf_index, channel, header[2];
    if (mDataSource->readAt(offset + 2, &header, 2) < 2) {
        return;
    }

    profile = (header[0] >> 6) & 0x3;
    sf_index = (header[0] >> 2) & 0xf;
    uint32_t sr = get_sample_rate(sf_index);
    if (sr == 0) {
        return;
    }
    channel = (header[0] & 0x1) << 2 | (header[1] >> 6);

    mMeta = AMediaFormat_new();
    MakeAACCodecSpecificData(mMeta, profile, sf_index, channel);
    AMediaFormat_setInt32(mMeta, AMEDIAFORMAT_KEY_AAC_PROFILE, profile + 1);

    off64_t streamSize, numFrames = 0;
    size_t frameSize = 0;
    int64_t duration = 0;

    if (mDataSource->getSize(&streamSize) == OK) {
         while (offset < streamSize) {
            if ((frameSize = getAdtsFrameLength(source, offset, NULL)) == 0) {
                ALOGW("prematured AAC stream (%lld vs %lld)",
                        (long long)offset, (long long)streamSize);
                break;
            }

            mOffsetVector.push(offset);

            offset += frameSize;
            numFrames ++;
        }

        // Round up and get the duration
        mFrameDurationUs = (1024 * 1000000ll + (sr - 1)) / sr;
        duration = numFrames * mFrameDurationUs;
        AMediaFormat_setInt64(mMeta, AMEDIAFORMAT_KEY_DURATION, duration);
    }

    mInitCheck = OK;
}

AACExtractor::~AACExtractor() {
    AMediaFormat_delete(mMeta);
}

media_status_t AACExtractor::getMetaData(AMediaFormat *meta) {
    AMediaFormat_clear(meta);
    if (mInitCheck == OK) {
        AMediaFormat_setString(meta, AMEDIAFORMAT_KEY_MIME, MEDIA_MIMETYPE_AUDIO_AAC_ADTS);
    }

    return AMEDIA_OK;
}

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

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

    return new AACSource(mDataSource, mMeta, mOffsetVector, mFrameDurationUs);
}

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

    return AMediaFormat_copy(meta, mMeta);
}

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

// 8192 = 2^13, 13bit AAC frame size (in bytes)
const size_t AACSource::kMaxFrameSize = 8192;

AACSource::AACSource(
        DataSourceHelper *source,
        AMediaFormat *meta,
        const Vector<uint64_t> &offset_vector,
        int64_t frame_duration_us)
    : mDataSource(source),
      mMeta(meta),
      mOffset(0),
      mCurrentTimeUs(0),
      mStarted(false),
      mOffsetVector(offset_vector),
      mFrameDurationUs(frame_duration_us) {
}

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

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

    if (mOffsetVector.empty()) {
        mOffset = 0;
    } else {
        mOffset = mOffsetVector.itemAt(0);
    }

    mCurrentTimeUs = 0;
    mBufferGroup->add_buffer(kMaxFrameSize);
    mStarted = true;

    return AMEDIA_OK;
}

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

    mStarted = false;
    return AMEDIA_OK;
}

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

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

    int64_t seekTimeUs;
    ReadOptions::SeekMode mode;
    if (options && options->getSeekTo(&seekTimeUs, &mode)) {
        if (mFrameDurationUs > 0) {
            int64_t seekFrame = seekTimeUs / mFrameDurationUs;
            if (seekFrame < 0 || seekFrame >= (int64_t)mOffsetVector.size()) {
                android_errorWriteLog(0x534e4554, "70239507");
                return AMEDIA_ERROR_MALFORMED;
            }
            mCurrentTimeUs = seekFrame * mFrameDurationUs;

            mOffset = mOffsetVector.itemAt(seekFrame);
        }
    }

    size_t frameSize, frameSizeWithoutHeader, headerSize;
    if ((frameSize = getAdtsFrameLength(mDataSource, mOffset, &headerSize)) == 0) {
        return AMEDIA_ERROR_END_OF_STREAM;
    }

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

    frameSizeWithoutHeader = frameSize - headerSize;
    if (mDataSource->readAt(mOffset + headerSize, buffer->data(),
                frameSizeWithoutHeader) != (ssize_t)frameSizeWithoutHeader) {
        buffer->release();
        buffer = NULL;

        return AMEDIA_ERROR_IO;
    }

    buffer->set_range(0, frameSizeWithoutHeader);
    AMediaFormat *meta = buffer->meta_data();
    AMediaFormat_setInt64(meta, AMEDIAFORMAT_KEY_TIME_US, mCurrentTimeUs);
    AMediaFormat_setInt32(meta, AMEDIAFORMAT_KEY_IS_SYNC_FRAME, 1);

    mOffset += frameSize;
    mCurrentTimeUs += mFrameDurationUs;

    *out = buffer;
    return AMEDIA_OK;
}

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

static CMediaExtractor* CreateExtractor(
        CDataSource *source,
        void *meta) {
    off64_t offset = *static_cast<off64_t*>(meta);
    return wrap(new AACExtractor(new DataSourceHelper(source), offset));
}

static CreatorFunc Sniff(
        CDataSource *source, float *confidence, void **meta,
        FreeMetaFunc *freeMeta) {
    off64_t pos = 0;

    DataSourceHelper helper(source);
    for (;;) {
        uint8_t id3header[10];
        if (helper.readAt(pos, id3header, sizeof(id3header))
                < (ssize_t)sizeof(id3header)) {
            return NULL;
        }

        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;

        pos += len;

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

    uint8_t header[2];

    if (helper.readAt(pos, &header, 2) != 2) {
        return NULL;
    }

    // ADTS syncword
    if ((header[0] == 0xff) && ((header[1] & 0xf6) == 0xf0)) {
        *confidence = 0.2;

        off64_t *offPtr = (off64_t*) malloc(sizeof(off64_t));
        *offPtr = pos;
        *meta = offPtr;
        *freeMeta = ::free;

        return CreateExtractor;
    }

    return NULL;
}

static const char *extensions[] = {
    "aac",
    NULL
};

extern "C" {
// This is the only symbol that needs to be exported
__attribute__ ((visibility ("default")))
ExtractorDef GETEXTRACTORDEF() {
    return {
        EXTRACTORDEF_VERSION,
        UUID("4fd80eae-03d2-4d72-9eb9-48fa6bb54613"),
        1, // version
        "AAC Extractor",
        { .v3 = {Sniff, extensions} },
    };
}

} // extern "C"

} // namespace android