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Commit 77e8ae99 authored by James Dong's avatar James Dong
Browse files

When a request max file size is relatively small, don't store moov header at the 

beginning of a recorded mp4 file.

Trying to put the 'moov' box at the beginning of an mp4 file requires to reserve
some estimated space for 'moov'. The estimate can be larger or smaller than the
actual 'moov' size. When the estimate is larger, we could meet the file
size limit, although some space is wasted; but when the estimate is smaller than
the actual 'moov' size, we not only waste the reserved space but also have to
use extra space to write 'moov' space at the end of the file. In this case, often
the requested file size limit could be exceeded by a large margin.

This patch avoids putting the 'moov' box at the beginning when a file size limit
is explicitly requested.

Change-Id: I838443d08b5589f33f3c486c662195600e3edb9b
related-to-bug: 6697505
parent ea682976

media/libstagefright/MPEG4Writer.cpp

+25 −7
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ 


namespace android {



static const int64_t kMinStreamableFileSizeInBytes = 5 * 1024 * 1024;

static const int64_t kMax32BitFileSize = 0x007fffffffLL;

static const uint8_t kNalUnitTypeSeqParamSet = 0x07;

static const uint8_t kNalUnitTypePicParamSet = 0x08;
@@ -487,8 +488,16 @@ status_t MPEG4Writer::start(MetaData *param) { 
    CHECK_GT(mTimeScale, 0);

    ALOGV("movie time scale: %d", mTimeScale);



    mStreamableFile = true;

    mWriteMoovBoxToMemory = false;

    /*

     * When the requested file size limit is small, the priority

     * is to meet the file size limit requirement, rather than

     * to make the file streamable.

     */

    mStreamableFile =

        (mMaxFileSizeLimitBytes != 0 &&

         mMaxFileSizeLimitBytes >= kMinStreamableFileSizeInBytes);



    mWriteMoovBoxToMemory = mStreamableFile;

    mMoovBoxBuffer = NULL;

    mMoovBoxBufferOffset = 0;
@@ -504,11 +513,16 @@ status_t MPEG4Writer::start(MetaData *param) { 
        mEstimatedMoovBoxSize = estimateMoovBoxSize(bitRate);

    }

    CHECK_GE(mEstimatedMoovBoxSize, 8);

    if (mStreamableFile) {

        // Reserve a 'free' box only for streamable file

        lseek64(mFd, mFreeBoxOffset, SEEK_SET);

        writeInt32(mEstimatedMoovBoxSize);

        write("free", 4);



        mMdatOffset = mFreeBoxOffset + mEstimatedMoovBoxSize;

    } else {

        mMdatOffset = mOffset;

    }



    mOffset = mMdatOffset;

    lseek64(mFd, mMdatOffset, SEEK_SET);

    if (mUse32BitOffset) {
@@ -689,7 +703,7 @@ status_t MPEG4Writer::reset() { 
    lseek64(mFd, mOffset, SEEK_SET);



    const off64_t moovOffset = mOffset;

    mWriteMoovBoxToMemory = true;

    mWriteMoovBoxToMemory = mStreamableFile;

    mMoovBoxBuffer = (uint8_t *) malloc(mEstimatedMoovBoxSize);

    mMoovBoxBufferOffset = 0;

    CHECK(mMoovBoxBuffer != NULL);
@@ -1062,6 +1076,10 @@ bool MPEG4Writer::exceedsFileSizeLimit() { 
        nTotalBytesEstimate += (*it)->getEstimatedTrackSizeBytes();

    }



    if (!mStreamableFile) {

        // Add 1024 bytes as error tolerance

        return nTotalBytesEstimate + 1024 >= mMaxFileSizeLimitBytes;

    }

    // Be conservative in the estimate: do not exceed 95% of

    // the target file limit. For small target file size limit, though,

    // this will not help.