Home/News | About | Download | Documentation | Forum | Bug Reports | Contact | Donations | Consulting | Projects | Legal | Security | FATE


This forum has not been maintained for a long time and will probably get deleted in the near future.
For faster responses to your questions, please use StackOverflow instead and tag your questions with "FFmpeg".
If you need a backup of the posts from this forum, please contact me directly.

FFmpeg Multicast Transcode Quality and Bitrate

Discussions about problems encountered using ffmpeg.
Forum rules
FFmpeg is in a state of perpetual development and we do not currently have the person power to backport fixes to official releases. As such, if you wish to query or report a bug, you must try with the latest development branch revision of FFmpeg to confirm the issue still exists. The latest FFmpeg can be downloaded from here: http://www.ffmpeg.org/download.html

FFmpeg Multicast Transcode Quality and Bitrate

Postby Trey41123 » Thu Apr 20, 2017 4:37 pm

Hey, I am doing some testing with ffmpeg to transcode a mpegts multicast stream down to 192x192 at 15fps for an iptv application. I am using the following string, but am having trouble balancing the quality and the bitrate. I need the bitrate to stay below 250k, be fairly constant, and keep the quality as good as possible at the new resolution. I have tried the following and run into issues where the bitrate spikes when the crf isnt set to a poor quality. Any ideas?

ffmpeg -i udp:<originating multicast address> -c:v libx264 -s 192x192 -r 15 -preset placebo -crf 30 -b:v 200k keyint=1:min-keyint=1:scenecut=-1 -an -f mpegts udp:<output multicast address>

Thanks
Trey41123
 
Posts: 2
Joined: Thu Apr 20, 2017 3:17 pm

Re: FFmpeg Multicast Transcode Quality and Bitrate

Postby mulvya » Thu Apr 20, 2017 5:31 pm

Add -maxrate N -bufsize 2N where N is your bitrate ceiling.
mulvya
 
Posts: 566
Joined: Mon Oct 26, 2015 6:58 am

Re: FFmpeg Multicast Transcode Quality and Bitrate

Postby Trey41123 » Thu Apr 20, 2017 6:39 pm

mulvya wrote:Add -maxrate N -bufsize 2N where N is your bitrate ceiling.


Thanks, I added -maxrate 175k and bufsize 350k and I have some reasonable control over bitrate and the streaming is smooth.

The only issue that remains is that the output looks quite grainy compared to a vlc output of the same resolution. Any thoughts on what how I could clean that up? I've tried various crf settings and it looks the same on even the most lossless settings.
Trey41123
 
Posts: 2
Joined: Thu Apr 20, 2017 3:17 pm


Return to ffmpeg

Who is online

Users browsing this forum: Bing [Bot], Yahoo [Bot] and 6 guests