• Clément Bœsch's avatar
    avformat/vobsub: fix several issues. · dbfe6110
    Clément Bœsch authored
    Here is an extract of fate-samples/sub/vobsub.idx, with an additional
    text at the end of each line to better identify each bitmap:
    
        timestamp: 00:04:55:445, filepos: 00001b000 Ace!
        timestamp: 00:05:00:049, filepos: 00001b800 Wake up, honey!
        timestamp: 00:05:02:018, filepos: 00001c800 I gotta go to work.
        timestamp: 00:05:02:035, filepos: 00001d000 <???>
        timestamp: 00:05:04:203, filepos: 00001d800 Look after Clayton, okay?
        timestamp: 00:05:05:947, filepos: 00001e800 I'll be back tonight.
        timestamp: 00:05:07:957, filepos: 00001f800 Bye! Love you.
        timestamp: 00:05:21:295, filepos: 000020800 Hey, Ace! What's up?
        timestamp: 00:05:23:356, filepos: 000021800 Hey, how's it going?
        timestamp: 00:05:24:640, filepos: 000022800 Remember what today is? The 3rd!
        timestamp: 00:05:27:193, filepos: 000023800 Look over there!
        timestamp: 00:05:28:369, filepos: 000024800 Where are they going?
        timestamp: 00:05:28:361, filepos: 000025000 <???>
        timestamp: 00:05:29:946, filepos: 000025800 Let's go see.
        timestamp: 00:05:31:230, filepos: 000026000 I can't, man. I got Clayton.
    
    Note the two "<???>": they are basically split subtitles (with the
    previous one), which the dvdsub decoder is now supposed to reconstruct
    with a previous commit. But also note that while the first chunk has
    increasing timestamps,
    
        timestamp: 00:05:02:018, filepos: 00001c800
        timestamp: 00:05:02:035, filepos: 00001d000
    
    ...it's not the case of the second one (and this is not an exception in the
    original file):
    
        timestamp: 00:05:28:369, filepos: 000024800
        timestamp: 00:05:28:361, filepos: 000025000
    
    For the dvdsub decoder, they need to be "filepos'ed" ordered, but the
    FFDemuxSubtitlesQueue is timestamps ordered, which is the reason of the
    introduction of a sub sort method in the context, to allow giving
    priority to the position, and then the timestamps. With that change, the
    dvdsub decoder get fed with ordered packets.
    
    Now the packet size estimation was also broken: the filepos differences
    in the vobsub index defines the full data read between two subtitles
    chunks, and it is necessary to take into account what is read by the
    mpegps_read_pes_header() function since the length returned by that
    function doesn't count the size of the data it reads. This is fixed with
    the introduction of total_read, and {old,new}_pos. By doing this change,
    we can drop the unreliable len16 heuristic and simplify the whole loop.
    Note that mpegps_read_pes_header() often read more than one PES packet
    (typically in one call it can read 0x1ba and 0x1be chunk along with the
    relevant 0x1bd packet), which triggers the "total_read + pkt_size >
    psize" check. This is an expected behaviour, which could be avoided by
    having a more chunked version of mpegps_read_pes_header().
    
    The latest change is the extraction of each stream into its own
    subtitles queue. If we don't do this, the maximum size for a subtitle
    chunk is broken, and the previous changes can not work. Having each
    stream in a different queue requires some little adjustments in the
    seek code of the demuxer.
    
    This commit is only meaningful as a whole change and can not be easily
    split. The FATE test changes because it uses the vobsub demuxer.
    dbfe6110
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