Re: VP9 encoder in FFMpeg doesn't respect Constant Bitrate settings

[Devesh Mittal]

Hello Google team, 

Possible to help us out with our query? 

Thanks, 

Devesh

On Wed, Feb 24, 2021 at 7:49 PM Akshay Mittal <aks...@zaanu.com> wrote:

Hello WebM team,

I am trying to encode a live stream into VP9 with constant bitrate using FFMpeg.

I am using the instructions given here:

https://developers.google.com/media/vp9/bitrate-modes/#cbr_bitrate_mode_ffmpeg_examples

In particular I am using the following command (using VOD instead of Live Stream as a test):

ffmpeg -i screen-112s.mp4 -c:v vp9  -b:v 500k -minrate 500k -maxrate 500k -quality realtime -speed 8 -c:a libvorbis screen-112s-ffmpeg-cbr-500k.webm

I am expecting an output video bitrate of ~500kbps but the actual output is ~1800kbps.

I have tried many options on that page, but I am still not able to get the constant bitrate function to work.

I am using ffmpeg version 4.1.6-1~deb10u1

and libvpx-vp9 version 1.7.0

Please find the input file attached. Please let me know how to properly use CBR encoding with VP9 or point me to the correct resource.

Thank you

Akshay

 screen-112s.mp4

[Akshay Mittal]

[Kernel Kangaroo]

Did you get any feedback on this? I too am at a loss to understand how CBR works with VP9. I have been playing with gstreamer and ffmpeg. Gstreamer at least maps options against libvpx arguments. FFMpeg hides this through its own options.

[James Zern]

On Sat, Mar 6, 2021 at 4:21 PM Kernel Kangaroo <kernelk...@gmail.com> wrote:

Did you get any feedback on this? I too am at a loss to understand how CBR works with VP9. I have been playing with gstreamer and ffmpeg. Gstreamer at least maps options against libvpx arguments. FFMpeg hides this through its own options.

For reference, the ffmpeg option mapping is documented here:

https://ffmpeg.org/ffmpeg-codecs.html#libvpx

 

On Wednesday, February 24, 2021 at 1:24:44 PM UTC-8 Akshay Mittal wrote:

Hello WebM team,

I am trying to encode a live stream into VP9 with constant bitrate using FFMpeg.

I am using the instructions given here:

https://developers.google.com/media/vp9/bitrate-modes/#cbr_bitrate_mode_ffmpeg_examples

In particular I am using the following command (using VOD instead of Live Stream as a test):

ffmpeg -i screen-112s.mp4 -c:v vp9  -b:v 500k -minrate 500k -maxrate 500k -quality realtime -speed 8 -c:a libvorbis screen-112s-ffmpeg-cbr-500k.webm

I am expecting an output video bitrate of ~500kbps but the actual output is ~1800kbps.

I have tried many options on that page, but I am still not able to get the constant bitrate function to work.

I am using ffmpeg version 4.1.6-1~deb10u1

and libvpx-vp9 version 1.7.0

Please find the input file attached. Please let me know how to properly use CBR encoding with VP9 or point me to the correct resource.

Thank you

Akshay

 screen-112s.mp4

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