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Commit 983ab88e authored by Dongwon Kang's avatar Dongwon Kang
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To make SniffMP3() more concrete so that we can remove false-positve responses... 

To make SniffMP3() more concrete so that we can remove false-positve responses from MPEG-PS streams.

Note: current resync logic keeps searching mp3 frames until it meets a
valid one. This resync logic works well with seek() operation, but in
SniffMP3(), this may cause false-positive classification for the
following MPEG-PS file format.
  A possible MPEG-PS video file:
      [PS header]...[mp3 frame][mp3 frame] ...
  MP3 files:
      [ID3 tag][mp3 frame][mp3 frame] ...

BUG: 5104562
Change-Id: Idd5020723f7bdb2fefc2a63fc8651580fd644399
parent 7fa6e424

media/libstagefright/MP3Extractor.cpp

+16 −15
Original line number Diff line number Diff line
@@ -52,7 +52,10 @@ static bool Resync( 
        *post_id3_pos = 0;

    }



    bool resync_from_head = false;

    if (*inout_pos == 0) {

        resync_from_head = true;



        // Skip an optional ID3 header if syncing at the very beginning

        // of the datasource.
@@ -137,23 +140,21 @@ static bool Resync( 


        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)) {

        if ((match_header != 0 && (header & kMask) != (match_header & kMask))

                || !GetMPEGAudioFrameSize(header, &frame_size)) {

            if (resync_from_head) {

                // This isn't a valid mp3 file because it failed to detect

                // a header while a valid mp3 file should have a valid

                // header here.

                break;

            } else {

                ++pos;

                ++tmp;

                --remainingBytes;

                continue;

            }

        }



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