[FFmpeg-devel] [PATCH] Pass on position from ffmpeg to filters

[Michael Niedermayer]

On Sun, Jul 11, 2010 at 12:21:48AM +0200, V?ctor Paesa wrote:
> Hi,
> 
> On Sat, Jul 10, 2010 at 23:45, Michael Niedermayer wrote:
> > On Sat, Jul 10, 2010 at 11:10:30PM +0200, V?ctor Paesa wrote:
> >> Hi,
> >> ffplay already passes on the file position to filters, but ffmpeg does not.
> >>
> >> I run the patched ffmpeg on the files generated by 'make test':
> >> for i in tests/data/lavf/lavf.*
> >> do
> >> ? echo pos_$i
> >> ? ./ffmpeg -debug 1 -vframes 25 -i $i -vf null -y a.avi 2>&1 </dev/null
> >> done | grep pos
> >>
> >> For ASF, DV, FLV, GXF, MXF, SWF, y4m, the content of ist->st->cur_pkt.pos
> >> does not look a reliable position.
> >>
> >> Thanks in advance for your review,
> >> V?ctor
> >
> >> ?ffmpeg.c ? ? ? ? ? ? ? ? ?| ? ?5 ++++-
> >> ?libavfilter/vsrc_buffer.c | ? ?5 ++++-
> >> ?libavfilter/vsrc_buffer.h | ? ?2 +-
> >> ?3 files changed, 9 insertions(+), 3 deletions(-)
> >> ae2a17e652143de4ce4317537bcff1cbd4d3a040 ?ffmpeg.pos.1.diff
> >> Index: ffmpeg.c
> >> ===================================================================
> >> --- ffmpeg.c ?(revision 24162)
> >> +++ ffmpeg.c ?(working copy)
> >> @@ -1648,7 +1648,10 @@
> >> ? ? ? ? ? ? ?// add it to be filtered
> >> ? ? ? ? ? ? ?av_vsrc_buffer_add_frame(ist->input_video_filter, &picture,
> >> ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ist->pts,
> >> - ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ist->st->codec->sample_aspect_ratio);
> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ist->st->codec->sample_aspect_ratio,
> >> + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ist->st->cur_pkt.pos);
> >
> > this looks wrong, pos from the AVPacket you get from the demuxer/parser
> > should be used not some lavf internal one
> 
> Pity. Would the next patch be OK to document that this is lavf internal?
> 
> Index: libavformat/avformat.h
> ===================================================================
> --- libavformat/avformat.h      (revision 24162)
> +++ libavformat/avformat.h      (working copy)
> @@ -498,7 +498,7 @@
> 
>      AVMetadata *metadata;
> 
> -    /* av_read_frame() support */
> +    /* Only for av_read_frame() support. NOT PART OF PUBLIC API. */

id say
not supposed to be used by external applications, try to use something else
if possible

there may be situations where applications that do uncommon things need to
peek into these, i think ive seen a case where cur_dts was the only way to
get a hint of where one was exactly after a seek without demuxing packets


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I hate to see young programmers poisoned by the kind of thinking
Ulrich Drepper puts forward since it is simply too narrow -- Roman Shaposhnik
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