ffmpeg how modify the contrast with nvidia “hevc_nvenc” codec

[marco000]

Hi,

I need to adjust to contrast of some mkv file I have tried this code:

ffmpeg -y -vsync 0 -hwaccel cuda -hwaccel_output_format cuda -i title00.mkv  -c:v hevc_nvenc -b:v 5M  -vf eq=contrast=1.0   output.mkv

but I get this error:

Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scaler_0'
Error reinitializing filters!
Failed to inject frame into filter network: Function not implemented
Error while processing the decoded data for stream #0:0

If I run the some line without "-vf eq=contrast=1.0":

ffmpeg -y -vsync 0 -hwaccel cuda -hwaccel_output_format cuda -i title00.mkv  -c:v hevc_nvenc -b:v 5M    output.mkv

the command work and don't show any error message but don't allow me to adjust the contrast.

There is a way to modify the contrast with nvidia hevc_nvenc codec ?

Thanks !

[jagabo]

I don't use hevc_nvenc but try adding "-pix_fmt yuv420p" after "-vsync 0".

[Selur]

Remove "-hwaccel_output_format cuda " when you want to apply software based filters.

Cu Selur

[marco000]

Thank you, unfortunatenly if I add "-pix_fmt yuv420p" after "-vsync 0" I get

Option pixel_format not found.

If I remove "-hwaccel_output_format cuda" (and I don't change northing else) the speed is slower and change from 18x to 9x.

Probably encode via software.

I need to process 6 TB of video.

There is another way ?

[Selur]

Option pixel_format not found.

looks like you mistyped, 'pix_fmt' should be used not 'pixel_format'

There is another way ?

I think not.

[jagabo]

If I remove "-hwaccel_output_format cuda" (and I don't change northing else) the speed is slower and change from 18x to 9x.

Probably encode via software.

From what I've read (since my earlier reply) that option leaves the decompressed video in video memory. The CPU can't access that memory so CPU filters cannot be used on it. Removing that option causes the decompressed video to be copied back to CPU memory so the CPU can access it. Then when it's ready to be compressed it is copied back to video memory. That's the cause of the slowdown. Switching to CPU encoding would likely be a much bigger drop in performance (depending on encoder and settings).

https://developer.nvidia.com/blog/nvidia-ffmpeg-transcoding-guide/

There is another way ?

I don't now if there's any way to get the GPU to perform the contrast adjustment.

[Selur]

Last I checked (ffmpeg -filters) there were only hardware filters for overlay, yadif, thumbnail and scale,....

[marco000]

If the contrast or other setting is not make by GPU, this is not a problem becouse it is a fast operation.

The most important think is the encode / decode that must be done by GPU otherwise will be a high drop of performace.

Hope exist a solution.

[marco000]

Last I checked (ffmpeg -filters) there were only hardware filters for overlay, yadif, thumbnail and scale,....

Thanks !

how I can get this list ?

[jagabo]

I only saw scale_npp and transpose_npp in the ffmpeg filters doc:

https://ffmpeg.org/ffmpeg-filters.html#scale_005fnpp
https://ffmpeg.org/ffmpeg-filters.html#transpose_005fnpp

If the contrast or other setting is not make by GPU, this is not a problem becouse it is a fast operation.

It's the copy operations that are slowing it down:

Copy decompressed frame from video memory to CPU memory, apply CPU eq filter, copy frame from CPU memory back to GPU memory for compression.

[marco000]

just to let you known I have found the solution:

-vf hwdownload,format=nv12,eq=contrast=1,hwupload_cuda


in short: Add "hwdownload,format=nv12," before and ",hwupload_cuda" after my filter and work perfectly.

Thanks !

[jagabo]

How does the speed compare?

[Selur]

I assumed that this is what ffmpeg should have done in the background when without "-hwaccel_output_format cuda",....

[marco000]

here full command line:

ffmpeg -y -vsync 0 -hwaccel cuda -hwaccel_output_format cuda -i title00.mkv -an -sn -c:v:0 hevc_nvenc -cq 30 -vf hwdownload,format=nv12,eq=contrast=1.03,hwupload_c uda output_ottimale.mkv

there is no any speed drop (for some strange reason in this post cut "hwupload_cuda").

Only for my curiosity:

Someone have experience about option like these:

-rc-lookahead 32 -spatial-aq 1 ?

someone tell that improve the quality but I don't known if is true or not ? I have GTX 1060 6GB video card

[Selur]

you might want to read: https://docs.nvidia.com/video-technologies/video-codec-sdk/pdf/Using_FFmpeg_with_NVIDI...celeration.pdf
Both Lookahead and Adaptive Quantization (AQ) are explained there,...

[marco000]

Thanks !! I wlll follow this pdf file