[FFmpeg-user] vaapi_h264 encoding very low bitrate

[owen s]

Hi Mark,

You're correct in that increasing the framerate for the image input
increases the bitrate.

You also suggested lowering the gop, but that would cause issues if I am
trying to stream at these settings since the gop needs to be 2* framerate.

there's no way to have higher framerate w/ an input image is there?

On Wed, Jan 20, 2021 at 9:08 PM Mark Thompson <sw at jkqxz.net> wrote:

> On 19/01/2021 16:07, owen s wrote:
> > I am running this command with
> > ffmpeg -y -loglevel debug \
> > -vaapi_device /dev/dri/renderD128 \
> > -loop 1 -r 1 -i ./image.jpg -pix_fmt vaapi_vld \
> > -b:v 18000k -minrate 18000k \
> > -vf 'format=nv12|vaapi,hwupload,scale_vaapi=w=1280:h=720' \
> > -rc_mode 3 \
> > -r 30 -g 60 \
> > -c:v h264_vaapi -f flv /dev/null
> >
> > I am getting high encoding speed of greater than 3x but the bitrate is
> > terrible 350Kbits/s
> >
> > Why is that when I can get better encoding speeds using cpu? log file
> > http://0x0.st/-i2j.txt
>
> Given that you're encoding the same image repeatedly, most of the frames
> will be a trivial "this frame is the same as the previous one" which can be
> signalled with very few bits.
>
> If you want to push the bitrate up then either don't use the same frame
> repeatedly as input or decrease the gop size (-g option) so that it is
> forced to intra-code more frames (I would guess that at -g 1 it will
> probably be able to hit the 18M target).
>
> - Mark
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