[FFmpeg-devel] [PATCH] Add null video filter

[Christian Iversen]

On 2009-10-19 00:34, Vitor Sessak wrote:
> Michael Niedermayer wrote:
>> On Sun, Oct 18, 2009 at 11:21:57PM +0200, Stefano Sabatini wrote:
>>> On date Sunday 2009-10-18 22:34:39 +0200, Michael Niedermayer encoded:
>>>> On Sun, Oct 18, 2009 at 12:25:41PM +0200, Stefano Sabatini wrote:
>>>>> On date Thursday 2009-10-08 00:18:25 +0200, Michael Niedermayer
>>>>> encoded:
>>> [...]
>>>>>> probably ok if extensively tested (for example benchmarks that it
>>>>>> does not
>>>>>> cause slowdown which would be an indication of extra memcpy being
>>>>>> done
>>>>>> somewhere)
>>>>> With ffplay I didn't noticed significant slowdowns even with an insane
>>>>> number of null filters (256).
>>>>>
>>>>> But I noticed some slowdowns with ffmpeg, even with a relatively small
>>>>> number of null filters:
>>>>> 16: utime=4.876s
>>>>> 17: utime=6.368s
>>>>> 18: utime=9.501s
>>>>> 19: utime=15.745s
>>>>> 20: utime=28.246s
>>>>> 21: utime=53.067s
>>>>>
>>>>> With 32 null filters the process seems to hangs, a quick inspection
>>>>> with gdb revealed that the processing hangs in avfilter_poll_frame(),
>>>>> anyway since the problem is not related to the present filter I
>>>>> committed.
>>>> please elaborate
>>>> what did you test, if not what was be commited?
>>> With ffplay:
>>> ffplay in.avi -vfilters "null,null,null,...,null"
>>>
>>> With ffmpeg:
>>> ffmpeg -t 5 -i in.avi -vfilters "null,null,null,...,null" -y out.avi
>>>
>>> Note that even changing the filter (e.g. using vflip) I got the same
>>> behavior, so I concluded that the problem was not depending on the
>>> null filter.
>>
>> the commit of the null filter made the bug possible, so it is dependant
>> on it. IMHO it should not have been commited
>>
>>
>> either way a chain of null filters should not cause such exponential
>> slowdown, that is a very serious bug and i really think that should be
>> fixed before commiting more code. If not even reverting the null filter
>> commit.
>
> I took the liberty of committing a trivial patch fixing this bug.

Might we know what that patch consisted of? I'm sure several people are 
dying to know :)

-- 
Med venlig hilsen
Christian Iversen