On 8/29/25 15:17, Hervé ANSELME wrote:
Hi,
I guess there is also a ffmpeg issue, because with the libsvtav1 codec :
-> if I use the ffmpeg 6.1 release : the "-maxrate" parameter is allowed
-> whereas if I use the 8.0 release : the "-maxrate" parameter
triggers an error
and this, with the same video codec, libsvtav1.
That's why, in the command line below, there is no "-maxrate"
parameter : because it was with the 8.0 release.
Regards,
HA
------------------------------------------------------------------------
*From:* Nicolas Gaullier via ffmpeg-user <[email protected]>
*Sent:* Friday, August 29, 2025 13:51
Hello,
AFAIK, this is a libsvtav1 issue, not an ffmpeg issue.
The kind of setup and target you have is possible with libx264, for
example, but not with libsvtav1.
You can give a try to the CBR mode of libsvtav1, but it is very
restricted, it involves the low delay mode, I feel you won't be very
happy with the resulting quality, but actually you should obtain the
desired bitrate.
Nicolas
On 8/29/25 10:03, Hervé ANSELME via ffmpeg-user wrote:
>
> Hello all,
>
> I am using the release 8.0 of ffmpeg/ffprobe, running on Windows 11
Family OS.
>
> I executed the following command :
>
> ffmpeg -i "initial movie.mkv" -y -loglevel error -sn ^
> -map 0:a:0 -acodec aac -ar 44100 -b:a 128k ^
> -map 0:v:0 -vcodec libsvtav1 -vf "scale=768:432" -sws_flags
lanczos+accurate_rnd -b:v 1200k -minrate 1200k ^
> -svtav1-params
"lossless=lower:nal-hrd=cbr:force-cfr=1:vbv-maxrate=1200k:vbv-bufsize=2400k"
^
> -bufsize 2400k "final movie.mkv"
>
> then, to see the result in the final film, regarding the video
characteristics, I executed :
>
> ffprobe -v error -select_streams v -show_entries
stream=codec_name,width,height,avg_frame_rate -of
default=noprint_wrappers=1 "final movie.mkv"
>
> which result is :
>
> bit_rate=930911
> codec_name=av1
> width=768
> height=432
> avg_frame_rate=25/1
>
> which raises the question : how is it that there is such a large
difference, between the desired video bitrate (1200k) and the actual
video bitrate obtained (930911 = 930k) ?
>
> How should I modify my command line to obtain an effective video
bitrate that is, if not equal, at least as close as possible, to 1200k ?
>
> Thank you in advance for your replies and advices.
>
> Cdlt,
> HA
Hum, we are both top-posting, which is very bad, let's back to the ML
rules...
Well, I tried your command line with "maxrate" added, and the log seems
pretty clear:
"Svt[error]: Instance 1: Max Bitrate only supported with CRF mode"
So, bad settings and clear error message: there is no ffmpeg issue, here.
NB1: libsvtav1 is somewhat picky with its settings, be careful about it,
look for example at the source here:
https://gitlab.com/AOMediaCodec/SVT-AV1/-/blob/master/Docs/Parameters.md
NB2: For future support queries, please make sure there is no error in
your command line before posting. I mean, you should have noted the
"Error parsing option lossless: lower" etc., so please remove any
extraneous/confusing/unsupported parameter even if it is not the root of
the issue you ask support for.
Nicolas
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