[vlc-devel] [PATCH] Avcodec: limit the number of threads automatically selected to 12

[Sergio M. Ammirata, Ph.D.]

Just to clarify:

I just retested on a 2 CPU machine (core i7, 6 cores each with
multithreading enabled) which basically gives me 24 cores listed under
/proc/cpuinfo.

When I try to transcode mpeg2 to h264, I get this error repeating over and
over again in the debug log:

0x80f65f0] avcodec generic warning: cannot decode one frame (36036 bytes)
too many threads
mpeg_decode_postinit() failure
[0x80f65f0] avcodec generic warning: cannot decode one frame (2920 bytes)
too many threads
mpeg_decode_postinit() failure
[0x80f65f0] avcodec generic warning: cannot decode one frame (6972 bytes)
too many threads
mpeg_decode_postinit() failure


If I use --ffmpeg-threads to limit the number of threads then it works
according to this table:

Using --ffmpeg-threads=16 or less, it works.
Using --ffmpeg-threads=17 or more, it does not work and I get the error
listed above.

This is consistent with J-B's statement regarding ffmpeg limit of 16
threads.

Sergio

On 12/29/11 3:07 PM, "Rafaël Carré" <funman at videolan.org> wrote:

>Le 11-12-29 04:36, Hugo Beauzée-Luyssen a écrit :
>> On Thu, Dec 29, 2011 at 10:25 AM, Jean-Baptiste Kempf <jb at videolan.org>
>>wrote:
>>> On Wed, Dec 28, 2011 at 11:59:49PM -0500, Rafaël Carré wrote :
>>>> Le 2011-12-28 21:08, Jean-Baptiste Kempf a écrit :
>>>>> It seems that over 16 doesn't behave well. Reduce it further for
>>>>>safety
>>>>
>>>> What is the problem exactly ?
>>>
>>> According to ringo, it doesn't work at all with 24 threads. According
>>>to
>>> the source, 16 threads is the maximum anyway.
>>>
>>> Best regards,
>>>
>> 
>> Doesn't work for me with ffmpeg-threads > 5, on a quad core.
>
>5 does work?
>
>What is the error, the assertion that Denis reported?
>
>IIRC ringo had a different problem and he couldn't give much details
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