[FFmpeg-user] When will ffmpeg use VP9 v1.5?
dcmhoybdpzkh at web.de
Tue Nov 24 15:47:57 CET 2015
On 24.11.2015 15:02, Moritz Barsnick wrote:
> Hi D,
> On Tue, Nov 24, 2015 at 14:31:58 +0100, D wrote:
>> I played setting the values higher but it was neither faster nor slower.
>> Average 4 cores utilization is still ~80%.
> BTW, how do you define "utilization"? I believe in "top", 100% equals
> one core's usage, so you should be able to achieve 400%. Below, you use
> the term "100% on all 4 cores".
The 80% figure was a bit too high BTW, it's rather between 60 and 75%.
In top it jumps between ~230 and ~270%.
> That said: I don't know much about libvpx, but this page:
> and more explicitly this one:
> says to use "-tile-columns" along with "-threads".
> -tile-columns slightly affects output quality but it's the only
> mechanism in VP9 to provide multithread encoding and decoding.
> According to that, "-tile-columns" apparently defaults to 6. OTOH
> "ffmpeg -h" says "-1", which corresponds to not explicitly setting it
> to the encoder. And according to the encoder's sources:
>> By default, the value is 0, i.e. one single column tile for entire
> So 6 (correspnding to 2^6 columns) is likely not the default, but 0
> (corresponding to 1 column), which is not beneficial to threading.
> Disclaimer, again: I know nothing much about libvpx or VP9. ;-)
Changing "-tile-columns" to 0 does indeed use only on core (100%).
Setting it to 6 (maximal value), does not change anything (maybe because
6 is already the default value if it is correct). Other values do not
improve the 60-75% figure (that's all 4 cores or ~250% in top) too.
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