[FFmpeg-devel] [PATCH] lavfi: dump debug graph when merging failed.

[Stefano Sabatini]

On date Monday 2013-12-02 19:11:33 +0100, Nicolas George encoded:
> Le duodi 12 frimaire, an CCXXII, Stefano Sabatini a écrit :
> > ffplay test.wav -af volume -loglevel debug
> 
> > [auto-inserted resampler 0 @ 0x7f929c01af20] Cannot select channel layout for the link between filters auto-inserted resampler 0 and ffplay_abuffersink.
> 
> > [AVFilterGraph @ 0x7f929c017720] 0: abuffer "ffplay_abuffer"
> > [AVFilterGraph @ 0x7f929c017720]   o0:0 ->i4:0 s16 / 44100 Hz / 2 channels
> > [AVFilterGraph @ 0x7f929c017720] 1: abuffersink "ffplay_abuffersink"
> > [AVFilterGraph @ 0x7f929c017720]   i1:0 <-o3:0 { same as o3:0 } /  { 44100 } / { all layouts and counts }
> > [AVFilterGraph @ 0x7f929c017720] 2: volume "Parsed_volume_0"
> > [AVFilterGraph @ 0x7f929c017720]   i2:0 <-o4:0 { same as o4:0 } / { same as i3:0 } / { all layouts }
> > [AVFilterGraph @ 0x7f929c017720]   o2:0 ->i3:0 { same as o4:0 } / { same as i3:0 } / { same as i2:0 }
> > [AVFilterGraph @ 0x7f929c017720] 3: aresample "auto-inserted resampler 0"
> > [AVFilterGraph @ 0x7f929c017720]   i3:0 <-o2:0 { same as o4:0 } /  { 44100 } / { same as i2:0 }
> > [AVFilterGraph @ 0x7f929c017720]   o3:0 ->i1:0  { s16 } / { same as i1:0 } / { same as i1:0 }
> > [AVFilterGraph @ 0x7f929c017720] 4: aresample "auto-inserted resampler 1"
> > [AVFilterGraph @ 0x7f929c017720]   i4:0 <-o0:0 s16 / 44100 Hz / 2 channels
> > [AVFilterGraph @ 0x7f929c017720]   o4:0 ->i2:0  { flt | fltp } / { same as i3:0 } / { same as i2:0 }
> > Failed to open file 'test.wav' or configure filtergraph
> > [AVIOContext @ 0x7f929c005620] Statistics: 917504 bytes read, 0 seeks
> > 
> > Do you manage to understand what's going on here? The input file has
> > unspecified channel layout.
> 
> That is exactly the kind of problems this patch aims to help understanding.
> The error message tells you the problem is at "auto-inserted resampler 1"

> and is about the channel layout. You can see the input channel layout has
> been selected as "2 channels" while the output is still open as { same as
> i2:0 }, which is { all layouts } because of volume: volume requires a
> specified layout.

Can you programmatically check and report this issue?

Also it would help:
iN => inN
oN => outN

oM ->iN => oM -> iN
iM <-oN => iM <- oN
(added spaces)
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