theora - Feb 2011 - Key frame bitrate

Hi,

I'm using Theora for live video chat. My problem is, at higher bitrates 
the bandwidth peaks caused by key frames are so high that most key 
frames get dropped in UDP traffic. The peaks are so strong that I still 
get many packet loss artifacts when sending with 1Mbit/s bitrate on a 
2Mbit/s connection. I measured delta frames to be around 12kbyte and key 
frames up to 100kbyte in 1280x720 video at 15fps even with lowest rate 
buffer settings.
I can send 2Mbit/s without errors when using heavy traffic shaping, but 
this causes clearly visible delay.
In pre-1.0 API there was a parameter to set the bitrate for key frames 
which would probably help a lot with this. Is there any chance key frame 
bitrate control finds its way back into Theora? Or any other workaround 
for this?

Thanks in advance
Andreas

On 8 February 2011 23:39, Andreas Engel <andreas.engel at bravis.eu>
wrote:
> I'm using Theora for live video chat. My problem is, at higher bitrates
> the bandwidth peaks caused by key frames are so high that most key
> frames get dropped in UDP traffic.
Have you tried TH_ENCCTL_SET_RATE_BUFFER to set the number of frames
over which the bitrate is averaged to a smaller number?

 -r

On Wed, Feb 9, 2011 at 2:39 AM, Andreas Engel <andreas.engel at bravis.eu>
wrote:
> Hi,
>
> I'm using Theora for live video chat. My problem is, at higher bitrates
> the bandwidth peaks caused by key frames are so high that most key
> frames get dropped in UDP traffic. The peaks are so strong that I still
> get many packet loss artifacts when sending with 1Mbit/s bitrate on a
> 2Mbit/s connection. I measured delta frames to be around 12kbyte and key
> frames up to 100kbyte in 1280x720 video at 15fps even with lowest rate
> buffer settings.
> I can send 2Mbit/s without errors when using heavy traffic shaping, but
> this causes clearly visible delay.
> In pre-1.0 API there was a parameter to set the bitrate for key frames
> which would probably help a lot with this. Is there any chance key frame
> bitrate control finds its way back into Theora? Or any other workaround
> for this?

What you probably want is "rolling intra" ? where there are no
periodic keyframes, only a band of keyblocks which moves across the
image refreshing it a part at a time.  I've been thinking about adding
this to libtheora.

If you have the time and interest to test this I can send you a patch
to libtheora which will provide this behavior. I'd like to hear how it
works in practice.