Vitor <[email protected]> added the comment:

On 07/29/2010 01:22 PM, Stefano Sabatini wrote:
> 
> Stefano Sabatini<[email protected]>  added the comment:
> 
> ffmpeg currently doesn't properly supports filtering with more than one 
> output.
> 
> Let's consider the command:
> ffmpeg -i INPUT OUTPUT1 OUTPUT2
> 
> INPUT has size wxh, OUTPUT1 has size w1xh1, OUTPUT2 has size w2xh2.
> 
> A filterchain is automatically added for scaling from the input to the output,
> in particular a scale filter is added to the end of the filter to rescale the
> decoded frame to the size requested by the output.
> The problem is that in this case the last scale filter will use the size w2xh2
> for both OUTPUT1 and OUTPUT2.
> 
> A possible solution requires the use of a distinct filterchain for each input
> and for each output.
> 
> This would allow for example to properly process a command of the kind:
> ffmpeg -vf IN_VF -i INPUT -vf OUT_VF1 OUTPUT1 -vf OUT_VF2 OUTPUT2

This seems less versatile than

ffmpeg -i INPUT -vf "[in] split [out1][out2]" OUTPUT1 OUTPUT2

that allows

ffmpeg -i INPUT -vf "[in] split [A1][A2]; [A1] filter1 [out1]; [A2] filter2
[out2]" OUTPUT1 OUTPUT2

But also allow several other funny tricks.

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<https://roundup.ffmpeg.org/issue2040>
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