Video encoding is single-threaded

[kallisti5]

Converting a video with MediaConverter results in a single thread being consumed. As FFMPEG supports multiple threads for encoding, this should be investigated. (or an option added to MediaConverter to specify threads)

[pulkomandy]

Does the ancinet version of ffmpeg we use support multiple threads, or is that a more recent addition to ffmpeg?

[korli]

For decoding it's done ​here. Now it's up to the encoder/decoder to actually use this setting.

[Barrett]

Isn't system_info.info.cpu_count set to the number of cpu cores? If i'm right, it's actually the expected way to work, and there's not any advantage on raw calculus to increase or decrease the number of threads behind.

[pulkomandy]

That code is only for decoding, we need to do the same for encoding (in AVCodecEncoder). As mentionned this also assumes ffmpeg will actually use the setting (it may not do so with some video formats).

[Barrett]

I was referring mostly to add it as a configurable option in MediaConverter. In the patch attached i've add the setting in the fContext of AVCodecEncoder and it adds two threads compared to the same rev built without it. The cores are more balanced, it can be seen in ProcessController where without the patch there's just one core in high load.

[Barrett]

There's anyway an accuracy drop when the patch is applied, it may be related to the comments contained in AVFormatReader.cpp. Our version of ffmpeg is also compiled without the --enable-pthread flag which may be cause of problems.

[pulkomandy]

What do you mean by "accuracy drop"? Is the encoding less good?

Another option could be to process several files at a time at MediaConverter side. This would be more generic and work also with other encoders, but help with MediaConverter only, and not with other apps.

[Barrett]

The resulting files played correctly in MediaPlayer but the image was visibly distorted with things like frames dropped. I think the result was different depending on the format, but it has passed a few time since i've tested it.

[pulkomandy]

Patch migrated to Gerrit: ​https://review.haiku-os.org/58

[waddlesplash]

Related: #11657.

[waddlesplash]

Patch was abandoned as it is not needed, FFmpeg does this already.

[nielx]

Remove milestone for tickets with status = closed and resolution != fixed