[FFmpeg-user] Use force_key_frames to obtain keyframes at exactly the same positions as in the input stream?

Henk D. Schoneveld belcampo at zonnet.nl
Sat May 2 21:32:59 CEST 2015

> On 02 May 2015, at 21:11, Anatol <anatol2002 at gmail.com> wrote:
> Henk,
> Its a real problem, if the streams are un-aligned, the playback gets into
> jump-forward-backward mood.
If you create a 5min source file and split in 5 1 minute chunks with the help of the hls function of ffmpeg.
Then create 3 other quality streams form these chunks.
This results in a total of 4 hls compatible streams where switching between each of them should be without any problem I think.
> It's not a problem to get source file key frames and to have them encoded
> into the rest of the files.
> The problem is with a live streaming, because it is not possible to query
> it for the keyframe lications
> Reuben,
> The whole idea is to avoid intense CPU consumption for LIVE streaming.
> On Sat, May 2, 2015 at 8:31 PM, Reuben Martin <reuben.m at gmail.com> wrote:
>> On Saturday, May 02, 2015 06:00:32 PM Haris Zukanovic wrote:
>>> My case is live streaming.
>>> I have tried it and definitely keyframes are not aligned between input
>>> and output streams.
>>> For all encoded output streams it is very simple to obtain alignement
>>> with setting the fixed GOP size. But the PTS and keyframes of input are
>>> never aligned with that.
>> I’ve had success with it as long as I encode all the derivative streams at
>> once from the same encoder process. This of course can consume significant
>> CPU
>> resources.
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