Hello Dan, Brian.
Thank you for your answers. I've been struggling with this issue for a
while and I don't manage to get an almost constant video bitrate in the
output.
It seems I should use the --nal-hrd cbr option to "fill the mux" as
explained in post:
http://forum.doom9.org/archive/index.php/t-159536.html
But I don't manage to use it successfully in Melt neither with -x264-params,
nor with x264opts.
I don't know how to properly translate it to "name=value" melt syntax.
Should I write -x264opts in the command or not?
I have made different tries with no success so far, such as:
vcodec=libx264 nal-hrd=cbr vbv-bufsize=6M vb=3M minrate=3M maxrate=3M g=15
bf=2 ts=cbr
Changing the line to:
vcodec=libx264 -x264opts nal-hrd=cbr vbv-bufsize=6M vb=3M minrate=3M
maxrate=3M g=15 bf=2 ts=cbr
does not seem to have effect either.
If I do: "melt -query consumer=avformat | grep x264"
It seems I have both options available:
- identifier: x264opts
description: x264 options (libx264)
description: Select the quality for constant quality mode (libx264)
- identifier: x264-params
description: "Override the x264 configuration using a :-separated list
of key=value parameters (libx264)"
description: Set the encoding preset (cf. x264 --fullhelp) (libx264rgb)
Do you have a melt working example to get a constant video bitrate in the
output?
Thank you,
David
On 30 March 2017 at 17:29, Dan Dennedy <d...@dennedy.org> wrote:
>
>
> On Thu, Mar 30, 2017 at 8:00 AM Brian Matherly <c...@brianmatherly.com>
> wrote:
>
>>
>> I need to get a true constant video bitrate in an UDP output address.
>>
>> By using cbrts consumer I am getting a constant muxrate in the UDP
>> output, but not a constant video bitrate.
>> I have noticed that varying the gop size has an effect in the shape of
>> the output video bitrate curve but still I am not getting a flat (or almost
>> flat) video bitrate line in the output analyzer.
>>
>> This is the script I am using:
>>
>> melt -profile atsc_1080i_50 test_1.mp4 \
>> -consumer cbrts udp.address=10.192.33.14 udp.port=5678 udp.ttl=12
>> udp.reuse=1 udp.rtp=0 muxrate=6000000 udp.buffer=1000 \
>> vcodec=libx264 bufsize=5505024 vb=3M minrate=3M maxrate=3M g=15 bf=2 \
>> acodec=mp2 ab=160k threads=3 real_time=1
>>
>> I am trying to add this libx264 encoding option
>>
>> -x264-params "nal-hrd=cbr:force-cfr=1"
>>
>> as described in this post:
>>
>> http://slhck.info/video/2017/03/01/rate-control.html
>>
>> but It seems that Melt is ignoring it although It is not showing any
>> error.
>>
>> Any help would be really appreciated!
>>
>> Regards,
>>
>> David
>>
>>
>> "-x264-params" is the "new" ffmpeg option. MLT still uses the old option:
>> "x264opts"
>> https://mltframework.org/plugins/ConsumerAvformat/#x264opts
>>
>> I suppose we will have to update to use the new option some day. In the
>> mean time, try using "x264opts".
>>
>>
> Actually, MLT does not define either x264-params or 264opts. Those are
> AVOptions that MLT exposes. So, it depends on how it is built (version of
> libavcodec). You can use "melt -query consumer=avformat | grep x264" to see
> which to use. Then, of course, you must use the melt "name=value" syntax
> instead of "-name value".
>
>
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