[vlc-devel] Sporadic-Frame Video Codec Problems

Michael Tänzer neo at nhng.de
Fri Jan 29 03:15:54 CET 2016


I'm still working on that OggSpots support. I went with just mangling it
in to the Ogg demuxer like all other codecs and I even get images out of
it (Yay!) but there are some remaining issues:

1. It seems that because the OggSpots codec only contains frames when
the content changes, the video stream is unhappy that it doesn't get
enough data. So it thinks that is some kind of Jitter, which means that
it calls input_clock_Reset() and that causes future target time
calculation on the picture_t.date to fail:
[00007f9f0cc25ad8] core decoder error: Timestamp conversion failed
(delay 300000, buffering 100000, bound 9000000)
[00007f9f0cc25ad8] core decoder error: Could not convert timestamp

2. Seeking is not possible. Probably because the packages are too far
apart, but I haven't really tried to pin this down. I wanted to solve
the other issue first:
[00007f9f0cc01b28] ogg demux error: Unmatched granule. New codec ?
[00007f9f140009d8] core input error: INPUT_CONTROL_SET_POSITION(_OFFSET)
11.9% failed

Can you point me into the right direction to solve this issue?

Approaches that came to my mind:
- Rewrite the codec as a subtitle codec instead of a video codec
(SPU_ES, SUBCAT_INPUT_SCODEC). But does VLC display such a codec if
there is no video stream? Are there other issues to be aware of that
come with this approach?
- There might be some setting that I missed so far that allows me to
signal to the video output that there is no problem if there is not a
constant stream of frames.
- Copy the last image into the stream whenever we need one and we
haven't encountered a fresh one. But how can this copying be triggered?
The DecodeBlock is only called if there is a new block from the demuxer,
not when there is the need for a picture.


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