Preview conversion not very efficient - not using all CPU cores

[geogan]

Converting preview is not very efficient. Only utilizing maybe 2 cores only (looks like 4 threads).

I want to use to chop up relevant parts of some 4K security footage which is in HEVC format as below

Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom (isom/iso2/mp41)
File size                                : 8.70 GiB
Duration                                 : 2 h 27 min
Overall bit rate                         : 8 452 kb/s

Video
ID                                       : 1
Format                                   : HEVC
Format/Info                              : High Efficiency Video Coding
Format profile                           : Main@L5@High
Codec ID                                 : hvc1
Codec ID/Info                            : High Efficiency Video Coding
Duration                                 : 2 h 27 min
Bit rate                                 : 8 392 kb/s
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 10.000 FPS
Minimum frame rate                       : 9.615 FPS
Maximum frame rate                       : 40.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Bits/(Pixel*Frame)                       : 0.101
Stream size                              : 8.63 GiB (99%)
Language                                 : English
Color range                              : Full
Color primaries                          : BT.709
Transfer characteristics                 : BT.709
Matrix coefficients                      : BT.709
Codec configuration box                  : hvcC

Doing the "high quality + audio" preview option, I can see 5950X utilisation of only 4 threads out of 32 possible and 16-18% usage only.

So converting 4K 2 hour footage is slow even on 5950X.

Is there not a multi-core FFMPEG available? This sort of job would be much better suited offloaded to an NVidia GPU to really speed it up. Or even better, native HEVC playback and preview using GPU decoding in the program?

[geogan]

This is CPU usage during "Slow" preview generation on 5950X

[geogan]

I found that the generated 375MB "slow quality" preview did not even play back properly in the program after generation either. And the quality was terrible in it (played using KMPlayer externally).

"Slow" Preview file format

Format                                   : Matroska
Format version                           : Version 4
File size                                : 367 MiB
Duration                                 : 2 h 27 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 348 kb/s
Writing application                      : Lavf58.45.100
Writing library                          : Lavf58.45.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : Theora
Codec ID                                 : V_THEORA
Duration                                 : 2 h 27 min
Width                                    : 712 pixels
Height                                   : 400 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Original frame rate                      : 29.970 FPS
Compression mode                         : Lossy
Writing library                          : Xiph.Org libtheora 1.2.0alpha 20100924 (Ptalarbvorm)
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio
ID                                       : 2
Format                                   : FLAC
Format/Info                              : Free Lossless Audio Codec
Codec ID                                 : A_FLAC
Duration                                 : 2 h 27 min
Bit rate mode                            : Variable
Channel(s)                               : 2 channels
Channel layout                           : L R
Sampling rate                            : 11.025 kHz
Bit depth                                : 24 bits
Compression mode                         : Lossless
Writing library                          : Lavc58.91.100 flac
Language                                 : English
Default                                  : Yes
Forced                                   : No

[geogan]

Actually I just found that the "Slowest" quality mode DOES actually use all CPU cores it seems... still I can see the progress is much slower than the "Slow" mode.

[geogan]

The SLOW mode on this video file processing time:

Started: 13.45

Finished: 17.37

Total: 3h 53m

Preview is more or less same size and resolution and still not that smooth in operation.

Format                                   : Matroska
Format version                           : Version 4
File size                                : 8.29 GiB
Duration                                 : 2 h 27 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 8 047 kb/s
Writing application                      : Lavf58.45.100
Writing library                          : Lavf58.45.100
ErrorDetectionType                       : Per level 1

Video
ID                                       : 1
Format                                   : VP9
Codec ID                                 : V_VP9
Duration                                 : 2 h 27 min
Width                                    : 3 840 pixels
Height                                   : 2 160 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Writing library                          : Lavc58.91.100 libvpx-vp9
Language                                 : English
Default                                  : Yes
Forced                                   : No

Audio
ID                                       : 2
Format                                   : FLAC
Format/Info                              : Free Lossless Audio Codec
Codec ID                                 : A_FLAC
Duration                                 : 2 h 27 min
Bit rate mode                            : Variable
Channel(s)                               : 1 channel
Channel layout                           : C
Sampling rate                            : 16.0 kHz
Bit depth                                : 24 bits
Compression mode                         : Lossless
Writing library                          : Lavc58.91.100 flac
Language                                 : English
Default                                  : Yes
Forced                                   : No

[mifi]

I did a test with changing codec to vpx-vp9, due to license uncertainties around GPL. I think this is why it's slow. Because vpx is a pretty slow codec. Will change back to x264, which should use all cores and be a LOT faster. (this can be confirmed by testing an older version of losslesscut.)

Planning on changing lossless-cut to GPL also, so that licenses are in order.

[geogan]

OK. Not sure what conversion code you use.... FMPEG lib? Maybe you could look into using a hardware accelerated version of the lib. One that uses NVidia GPU cores to do conversion would be a lot quicker than any CPU based conversion (same as Adobe did in Premiere)

[mifi]

Turns out that ffmpeg does indeed support hardware encoding with Nvidia. I created a feature request for it here:
#835