From 97f2fb5bc753f021bfa51f58129bc1a36c047c47 Mon Sep 17 00:00:00 2001 From: Dongwon Kang Date: Thu, 18 Aug 2011 15:24:27 +0900 Subject: 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 --- media/libstagefright/MP3Extractor.cpp | 31 ++++++++++++++++--------------- 1 file changed, 16 insertions(+), 15 deletions(-) (limited to 'media/libstagefright/MP3Extractor.cpp') diff --git a/media/libstagefright/MP3Extractor.cpp b/media/libstagefright/MP3Extractor.cpp index 92e84c2..09f91f5 100644 --- a/media/libstagefright/MP3Extractor.cpp +++ b/media/libstagefright/MP3Extractor.cpp @@ -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. @@ -137,22 +140,20 @@ 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)) { - ++pos; - ++tmp; - --remainingBytes; - continue; + 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); -- cgit v1.1