Lossless round trip RGB24 - NVENC_HEVC - RGB24

[qo4on]

I know that to get 8 bit rgb I need to use a 10 bit or more yuv. I couldn't find yuv444p10le, so I chose yuv444p16le (but ffprobe shows yuv444p10le anyway).

ffmpeg -y -vsync 0 -i %01d.png -pix_fmt yuv444p16le -c:v hevc_nvenc -tune lossless out.mov
ffmpeg -i out.mov -pix_fmt rgb24 img/out-%03d.png
ffmpeg -i img/out-%03d.png -i %01d.png -filter_complex ssim -f null -
SSIM R:0.999988 (49.290492) G:1.000000 (inf) B:0.999971 (45.373878) All:0.999986 (48.665779)

The result is not lossless. What am I doing wrong?

[pandy]

I know that to get 8 bit rgb I need to use a 10 bit or more yuv. I couldn't find yuv444p10le, so I chose yuv444p16le (but ffprobe shows yuv444p10le anyway).

ffmpeg -y -vsync 0 -i %01d.png -pix_fmt yuv444p16le -c:v hevc_nvenc -tune lossless out.mov
ffmpeg -i out.mov -pix_fmt rgb24 img/out-%03d.png
ffmpeg -i img/out-%03d.png -i %01d.png -filter_complex ssim -f null -
SSIM R:0.999988 (49.290492) G:1.000000 (inf) B:0.999971 (45.373878) All:0.999986 (48.665779)

The result is not lossless. What am I doing wrong?

Verify supported pixel formats and encoder options with help of:

ffmpeg -h encoder=hevc_nvenc >hevc_nvenc.txt

Verify if HEVC lossless is supported by your NVEnc (IIRC only Pascal and newer silicone is capable to do so).

[qo4on]

Supported pixel formats: yuv420p nv12 p010le yuv444p p016le yuv444p16le bgr0 rgb0 cuda d3d11

  -tune              <int>        E..V....... Set the encoding tuning info (from 1 to 4) (default hq)
     lossless        4            E..V....... Lossless

I use GTX 1060, it is Pascal. So, everything seems to be ok.

[pandy]

run ffmpeg with report active - perhaps some color space conversion is applied automatically - ffmpeg can do such things without notification...

you can try to use zscale or colorspace video filter to manually manage all this - also for lossless RGB conversion i would use personally YCgCo color space instead YUV (qood question if nvenc can be faked to use YCgCo as YUV)

[qo4on]

I don't know what to do about it:

cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
[graph 0 input from stream 0:0 @ 00000272c1abc140] Setting 'video_size' to value '1920x1080'
[graph 0 input from stream 0:0 @ 00000272c1abc140] Setting 'pix_fmt' to value '26'
[graph 0 input from stream 0:0 @ 00000272c1abc140] Setting 'time_base' to value '1/25'
[graph 0 input from stream 0:0 @ 00000272c1abc140] Setting 'pixel_aspect' to value '3780/3780'
[graph 0 input from stream 0:0 @ 00000272c1abc140] Setting 'frame_rate' to value '25/1'
[graph 0 input from stream 0:0 @ 00000272c1abc140] w:1920 h:1080 pixfmt:rgba tb:1/25 fr:25/1 sar:3780/3780
[format @ 00000272c1abc800] Setting 'pix_fmts' to value 'yuv444p16le'
[auto_scaler_0 @ 00000272c1abc900] Setting 'flags' to value 'bicubic'
[auto_scaler_0 @ 00000272c1abc900] w:iw h:ih flags:'bicubic' interl:0
[format @ 00000272c1abc800] auto-inserting filter 'auto_scaler_0' between the filter 'Parsed_null_0' and the filter 'format'
[AVFilterGraph @ 00000272c1ab6900] query_formats: 4 queried, 2 merged, 1 already done, 0 delayed
[auto_scaler_0 @ 00000272c1abc900] w:1920 h:1080 fmt:rgba sar:3780/3780 -> w:1920 h:1080 fmt:yuv444p16le sar:1/1 flags:0x4

[pandy]

Try to verify steps so for example at first skip nvenc, secondly use software x265 - perhaps nvenc is not lossless...

[qo4on]

x265 shows the same result.

[poisondeathray]

x265 shows the same result.

libx265 is ok on 1.png

ffmpeg -i 1.png -vf scale=out_color_matrix=bt709,format=yuv444p10le -c:v libx265 -x265-params lossless=1 libx265.mp4
ffmpeg -i libx265.mp4 -vf scale=in_color_matrix=bt709,format=rgb24 libx265_to_png.png
ffmpeg -i libx265_to_png.png -i 1.png -filter_complex ssim -f null -

[Parsed_ssim_0 @ 000000b166aa1d40] SSIM R:1.000000 (inf) G:1.000000 (inf) B:1.000000 (inf) All:1.000000 (inf)

[pandy]

Will you be able to compare source and decoded result (for example by subtracting) it could be interesting to check whether issue is in levels or in edges (simplification for this discussion).
Alternatively you can try to sent RGB without conversion to YUV - perhaps this can be issue.

Of course as always with NVEnc you should use latest NVidia API version.

[qo4on]

ffmpeg -i 1.png -vf scale=out_color_matrix=bt709,format=yuv444p10le -c:v libx265 -x265-params lossless=1 libx265.mp4
ffmpeg -i libx265.mp4 -vf scale=in_color_matrix=bt709,format=rgb24 libx265_to_png.png

Thank you! You are right. Your settings are truly lossless, all pixels are exactly the same with a difference of 0. Nvenc is also lossless.

Do you know why ffmpeg uses yuv444p16le even though I specified yuv444p10le? Although checking after conversion with ffprobe shows that the file is yuv444p10le:

ffmpeg -y -r 60 -i %01d.png -vf scale=out_color_matrix=bt709,format=yuv444p10le -c:v hevc_nvenc -tune lossless out.mov

Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> hevc (hevc_nvenc))
Press [q] to stop, [?] for help
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
cur_dts is invalid st:0 (0) [init:0 i_done:0 finish:0] (this is harmless if it occurs once at the start per stream)
[Parsed_scale_0 @ 000002470b93d840] Setting 'out_color_matrix' to value 'bt709'
[Parsed_scale_0 @ 000002470b93d840] Setting 'flags' to value 'bicubic'
[Parsed_scale_0 @ 000002470b93d840] w:iw h:ih flags:'bicubic' interl:0
[Parsed_format_1 @ 000002470b93c7c0] Setting 'pix_fmts' to value 'yuv444p10le'
[graph 0 input from stream 0:0 @ 000002470b9bac40] Setting 'video_size' to value '1920x1080'
[graph 0 input from stream 0:0 @ 000002470b9bac40] Setting 'pix_fmt' to value '26'
[graph 0 input from stream 0:0 @ 000002470b9bac40] Setting 'time_base' to value '1/60'
[graph 0 input from stream 0:0 @ 000002470b9bac40] Setting 'pixel_aspect' to value '3780/3780'
[graph 0 input from stream 0:0 @ 000002470b9bac40] Setting 'frame_rate' to value '60/1'
[graph 0 input from stream 0:0 @ 000002470b9bac40] w:1920 h:1080 pixfmt:rgba tb:1/60 fr:60/1 sar:3780/3780
[format @ 000002470b9bb080] Setting 'pix_fmts' to value 'yuv420p|nv12|p010le|yuv444p|p016le|yuv444p16le|bgr0|rgb0|cuda|d3d11'
[auto_scaler_0 @ 000002470b9bb600] Setting 'flags' to value 'bicubic'
[auto_scaler_0 @ 000002470b9bb600] w:iw h:ih flags:'bicubic' interl:0
[format @ 000002470b9bb080] auto-inserting filter 'auto_scaler_0' between the filter 'Parsed_format_1' and the filter 'format'
[AVFilterGraph @ 000002470b937280] query_formats: 5 queried, 3 merged, 1 already done, 0 delayed
[auto_scaler_0 @ 000002470b9bb600] picking yuv444p16le out of 8 ref:yuv444p10le alpha:0
[Parsed_scale_0 @ 000002470b93d840] w:1920 h:1080 fmt:rgba sar:3780/3780 -> w:1920 h:1080 fmt:yuv444p10le sar:1/1 flags:0x4
[auto_scaler_0 @ 000002470b9bb600] w:1920 h:1080 fmt:yuv444p10le sar:1/1 -> w:1920 h:1080 fmt:yuv444p16le sar:1/1 flags:0x4

  Stream #0:0: Video: hevc (Rext) (hev1 / 0x31766568), yuv444p16le(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 2000 kb/s, 60 fps, 15360 tbn

ffprobe
  Stream #0:0: Video: hevc (Rext) (hev1 / 0x31766568), yuv444p10le(tv, progressive), 1920x1080 [SAR 1:1 DAR 16:9], 67964 kb/s, 60 fps, 60 tbr, 15360 tbn, 60 tbc (default)

[qo4on]

Another question. libx265 outputs 8-bit lossless rgb hevc video:

ffmpeg -y -r 60 -i %01d.png -c:v libx265 -x265-params lossless=1 out.mov
Stream #0:0: Video: hevc (Rext) (hev1 / 0x31766568), gbrp(pc, gbr/unknown/unknown, progressive), 1920x1080, 9468 kb/s, 60 fps, 60 tbr, 15360 tbn, 60 tbc (default)

Is there hevc_nvenc alternative for this command? So, it would be possible to get 8-bit lossless video without using 10-bit files.

hevc_nvenc supports: yuv420p nv12 p010le yuv444p p016le yuv444p16le bgr0 rgb0 cuda d3d11
I tried:

ffmpeg -y -r 60 -i %01d.png -vf format=rgb0 -c:v hevc_nvenc -tune lossless out.mov

But it outputs yuvj420p, which is not lossless.

[poisondeathray]

AFAIK, RGB output is not supported by NVEnc