[FFmpeg-trac] #11196(avformat:new): ffmpeg is unable to identify/open mpeg 2/3 files with only one frame

[FFmpeg]

#11196: ffmpeg is unable to identify/open mpeg 2/3 files with only one frame
-------------------------------------+-------------------------------------
             Reporter:  Greisberger  |                     Type:  defect
  Christophe                         |
               Status:  new          |                 Priority:  normal
            Component:  avformat     |                  Version:
                                     |  unspecified
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 How to reproduce:
 {{{
 % ffmpeg -i input.21 output.wav
 [mp3 @ 000001A7C88A2C00] Format mp3 detected only with low score of 1,
 misdetection possible!
 [mp3 @ 000001A7C88A2C00] Invalid frame size (768): Could not seek to 768.
 [in#0 @ 000001A7C887E040] Error opening input: Invalid argument
 Error opening input file input.21.
 Error opening input files: Invalid argument
 }}}

 I tracked the problem in `libavformat/mp3_dec.c` here:
 {{{
 mp3_read_header(AVFormatContext *s)
 {
    ...
             ffio_ensure_seekback(s->pb, i + 1024 + frame_size + 4);
             ret = check(s->pb, off + i + frame_size, &header2);
             if (ret >= 0 &&
                 (header & MP3_MASK) == (header2 & MP3_MASK))
             {
                 break;
             } else if (ret == CHECK_SEEK_FAILED) {
                 av_log(s, AV_LOG_ERROR, "Invalid frame size (%d): Could
 not seek to %"PRId64".\n", frame_size, off + i + frame_size);
                 return AVERROR(EINVAL);
             }
 }}}

 It seeks to the end of the 1st (any unique) frame, then fails to read 4
 bytes (of course).

 With files with at least 2 frames, it works
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11196>
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