[FFmpeg-devel] [PATCH 7/7] lavfi/vf_stack: move to activate design.

Nicolas George george at nsup.org
Sun Aug 6 18:33:58 EEST 2017

Le nonidi 19 thermidor, an CCXXV, John Warburton a écrit :
> Gentlemen, I am sorry to report that this particular patch to
> lavfi/vf_stack.c breaks FFmpeg on-screen output when a vertical stack
> (vstack) follows a horizontal stack (hstack). Below, please find a
> chain to -filter_complex, cut down from a much more complex chain,
> that reproduces the problem.
> FFmpeg here is compiled for Windows using mingw-w64 tool chain on Bash
> for Windows. I usually make this up nearly every day without incident.
> At commit 4e0e9ce2dc67a94c98d40a46e91fe5aa53ad0376 ("lavfi/framesync2:
> implement "activate" design"), the following script downloads an audio
> stream, and successfully produces three visual representations using
> FFmpeg filters, output to the 'SDL' device. 'opengl' also works.
> In this script, the avectorscope and showfreqs filters are
> horizontally stacked; then this combination is stacked vertically with
> an output from the ebur128 filter.
> ffmpeg -v debug -i 'http://s3.yesstreaming.net:7001/;stream/'
> -filter_complex "[a0]asplit=3[a][b][c];
> [a]avectorscope=size=512x512[z]; [b]showfreqs[y]; [z][y]hstack[n];
> [c]ebur128=video=1[d][e]; [d]scale=1536:512[g]; [n][g]vstack;
> [e]anullsink" -f SDL Test
> But once the patch to lavfi_vf_stack is applied, at commit
> 0dd8320e16bcdbe6b928e99489cf47abd16d3255, the same script results in a
> blank, white display window using the SDL device, and a blank black
> window using opengl. The text output from the ebur128 filter stops
> after one line. Merely applying a single hstack or vstack works: but
> the two together fail after this point:
> https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/0dd8320e16bcdbe6b928e99489cf47abd16d3255
> ("lavfi/vf_stack: move to "activate" design")
> Furthermore, compiling from today's git master but reversing ONLY the
> above patch to vf_stack.c also results in a working FFmpeg when given
> the above test case.

I can reproduce the issue here. Thanks for the report.


  Nicolas George
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