[FFmpeg-devel] eval lavfi filter

Wed Feb 25 23:54:26 CET 2009

On Wed, Feb 25, 2009 at 11:16:55PM +0100, V?ctor Paesa wrote:
> Hi,
> 
> Michael Niedermayer said:
> > On Wed, Feb 25, 2009 at 01:04:15PM +0100, V?ctor Paesa wrote:
> >> Hi,
> >> Michael Niedermayer said:
> >> > On Wed, Feb 25, 2009 at 09:07:57AM +0100, V?ctor Paesa wrote:
> >> >> Hi,
> >> >>
> >> >> Michael Niedermayer said:
> >> >> > On Tue, Feb 24, 2009 at 11:56:54PM +0100, Stefano Sabatini wrote:
> >> >> >> On date Tuesday 2009-02-24 23:26:23 +0100, Michael Niedermayer
> >> >> encoded:
> >> >> >> > On Tue, Feb 24, 2009 at 10:39:22PM +0100, Stefano Sabatini
> >> wrote:
> >> >> >> > > Hi.
> >> >> >> > >
> >> >> >> > > On date Tuesday 2009-01-20 09:37:21 +0100, V?ctor Paesa
> >> >> encoded:
> >> >> >> > > > There is also a problem for filters that remove frames, as
> >> >> >> ffmpeg uses/expects the fps of the input video (instead of the
> >> >> filtered one) and generates duplicated frames to reach that.
> >> >> >> >
> >> >> >> > ffmpeg should not duplicate frames anymore if the container
> >> can
> >> >> >> handle it
> >> >> >>
> >> >> >> Could someone give some more hints about this?
> >> >> >
> >> >> > just try the example that caused frame duplication and check the
> >> >> resulting file, avi/mov/mp4/nut should have no duplicate frames
> >> anymore. feedback and bugreports welcome ...
> >> >> >
> >> >> >
> >> >> >>
> >> >> >> Also I suppose this is not necessarily a lavfi-related issue,
> >> >> right?
> >> >> >
> >> >> > no
> >> >>
> >> >> Right, I was able to trace it (but not able to fix) to ffmpeg.c, it
> >> seems that do_video() is duplicating frames. Maybe adding a new
> >> "-vsync 3" that would not perfom any frame rate duplication?
> >> >
> >> > just tried
> >> > ffmpeg -v 9 -i matrixbench_mpeg2.mpg -r 90 test.avi
> >> >
> >> > no duplicated frames are generated and considering you provide not a
> >> single word of a hint of what you did or what did not work i cant
> >> help
> >>
> >> I'm sorry, I answered without reading your commit 17555, please
> >> discard my comments.
> >>
> >> Some tests on r17555:
> >>
> >> in.avi =
> >> http://samples.mplayerhq.hu/avi/fpstest/gwl-bounce-sample-25fps.avi
> >> that is 60 seconds long and has 1500 frames.
> >>
> >> $ ffmpeg  -i in.avi -vfilters fps=1 -y -an out_fps1.avi
> >> FFmpeg version SVN-r17555, Copyright (c) 2000-2009 Fabrice Bellard, et
> >> al.
> >>   configuration: --enable-shared --disable-static --cpu=prescott
> >> --extra-cflags=-DX_DISPLAY_MISSING -I/usr/local/include -include
> >> llrint.h --extra-ldflags=-L/usr/local/lib --extra-libs=-l llrint
> >> --enable-gpl --enable-nonfree --enable-libamr-nb --enable-libamr-wb
> >> --enable-swscale --enable-avfilter --enable-avfilter-lavf
> >> --enable-pthreads --enable-avisynth --enable-bzlib --enable-libfaac
> >> --enable-libgsm --enable-libmp3lame --enable-libtheora
> >> --enable-libx264 --enable-zlib --build-suffix=-SVN
> >>   libavutil     49.15. 0 / 49.15. 0
> >>   libavcodec    52.18. 0 / 52.18. 0
> >>   libavformat   52.29. 2 / 52.29. 2
> >>   libavdevice   52. 1. 0 / 52. 1. 0
> >>   libavfilter    0. 4. 0 /  0. 4. 0
> >>   libswscale     0. 7. 1 /  0. 7. 1
> >>   built on Feb 25 2009 11:41:58, gcc: 4.2.4
> >>
> >> Seems stream 0 codec frame rate differs from container frame rate:
> >> 30000.00 (30000/1) -> 25.00 (25/1)
> >> Input #0, avi, from 'in.avi':
> >>   Duration: 00:01:00.03, start: 0.000000, bitrate: 822 kb/s
> >>     Stream #0.0: Video: mpeg4, yuv420p, 640x352 [PAR 1:1 DAR 20:11],
> >> 25
> >> tbr, 25 tbn, 30k tbc
> >>     Stream #0.1: Audio: mp3, 22050 Hz, stereo, s16, 56 kb/s
> >> Output #0, avi, to 'out_fps1.avi':
> >>     Stream #0.0: Video: mpeg4, yuv420p, 640x352 [PAR 1:1 DAR 20:11],
> >> q=2-31, 200 kb/s, 90k tbn, 25 tbc
> >> Stream mapping:
> >>   Stream #0.0 -> #0.0
> >> Press [q] to stop encoding
> >> frame=   60 fps= 35 q=6.9 Lsize=     292kB time=59.04 bitrate=
> >> 40.5kbits/s video:252kB audio:0kB global headers:0kB muxing overhead
> >> 16.000823%
> >>
> >>
> >> The out_fps1.avi has 60 frames, as expected, but VirtualDub believes
> >> has 1476 frames due to the 25 tbc probably. GSpot reports 60 frames.
> >> ffmpeg is also confused and ffmpeg -i out_fps1.avi out%04d.png
> >> produces 1475 PNGs.
> >>
> >>
> >> ffmpeg  -i in.avi -vfilters fps=1 -r 1  -y -an out_fps1_r1.avi
> >>
> >> The out_fps1_r1.avi has 60 frames, works fine in VirtualDub, GSpot,
> >> ffmpeg.
> >
> > all mostly as expected, did you expect anything else?
> 
> Well, since avfilters may drop/add frames and alter timestamps, there
> should be some way to tell ffmpeg to avoid sync'ing against the
> original input stream.

i dont understand what you mean
if you want the timestamps of future frames decreased by "1" after a
droped frame, the drop filter surely can adjust the timestamps.
if its not that i dont understand what what you try to explain

> -r is a way, but it then forces a fixed rate.

there is always some rate, that may be 1/10000000 or 1/25 but there is
always one.
-r does not force fixed fps
-r X -vsync 1 does and vsync 1 was default a long time ago, vsync switched
to -1 as default and the behavior of -1 changed recently

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

I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20090225/cc67025a/attachment.pgp>