[FFmpeg-devel] [PATCH V2] lavc/libvpx: increase thread limit to 64

[Dmitrii Ovchinnikov]

>> Why do you still impose an upper limit unconditionally even if the
>>user has set his preferred number of threads?
Libvpx-vp9 does not support number of threads greater than 64, so we impose
an upper limit of 64.
E.g. if we set it any higher we get the following execution error:
[libvpx-vp9 @ 0x2f631c0] Failed to initialize encoder: Invalid parameter
[libvpx-vp9 @ 0x2f631c0]   Additional information: g_threads out of range
[..64]
Error initializing output stream 0:0 -- Error while opening encoder for
output stream #0:0 - maybe incorrect parameters such as bit_rate, rate,
width or height

>>According to
https://ffmpeg.org/pipermail/ffmpeg-devel/2018-November/236406.html the
>>maximum of 16 has not been chosen because of H.264, but because there
>>was some form of restriction in libvpx. Or at least there was belief in
>>the existence of such a restriction.
There is a restriction of maximum 64 threads, not 16.

>>This code potentially calls av_cpu_count() twice.
Can you please clarify how it calls it twice? Thanks.