[FFmpeg-devel] Live streaming of VP8

[Andy Bell]

On 9 Jun 2012, at 17:14, Michael Niedermayer <michaelni at gmx.at> wrote:

> On Sat, Jun 09, 2012 at 04:51:23PM +0200, Andy Bell wrote:
>> Hi All,
>> 
>> I am streaming a VP8 stream over network and using the following code to
>> encode:
>> 
>> _bitRate = 500 * 1000;
>> _codecContext->bit_rate = _bitRate; // --target-bitrate=500
>> _codecContext->rc_min_rate = _codecContext->rc_max_rate =
>> _codecContext->bit_rate; // --end-usage=cbr
>> 
>> _codecContext->thread_count = 4;
>> _codecContext->qmin = 4;
>> _codecContext->qmax = 56;
>> _codecContext->width = 800;
>> _codecContext->height = 600;
>> _codecContext->rc_buffer_aggressivity = 0.95;  // --undershoot-pct=95
>> _codecContext->rc_buffer_size = _bitRate * 6; // --buz-sz=6000 ms
>> _codecContext->rc_initial_buffer_occupancy = _bitRate * 4; //
>> --buf-initial-sz=4000 ms
>> _codecContext->profile = 3;
>> _codecContext->time_base.num = 1;
>> _codecContext->time_base.den = 25;
>> _codecContext->gop_size = 999999; // --kf-max-dist
>> 
>> This works fine but when there is a huge scene change the codec generates a
>> key frame which I am having trouble transmitting in realtime over the
>> network due to the sudden jump in bitrate.
> 
> rc_buffer_size indicates a wanted max latency of 6 seconds
> if you want it to be less you can use a smaller value
> 
> [...]
> 

Forgive my ignorance but can you explain why that would help?

Thanks, Andy