[FFmpeg-devel] H264 encoding and RTP muxing - calculating pts and dts

Vladimir Pantelic vladoman
Tue Jul 20 15:33:02 CEST 2010


Alexandre Ferrieux wrote:

> Side question: what is the behavior of ffmpeg when such a VFR input (assuming the grabbing rate is somehow irregular) is
> converted to a CFR container and codec like TS/mpeg2 ?
>
> Suppose an input timeline with frames F1...Fn. Dots indicate time:
>
>     F1.....F2....................F3....F4................F5
>
> and a regular output timeline for mpeg2ts:
>
>     G1.......G2.......G3.......G4.......G5.......G6.......G7
>
> What is G4:
>
>      - F2 (latest) ?
>      - F3 (closest, non-causal) ?
>      - F4 (one-to-one) ?

F4

>      - other ?

> Also, would it be possible to tell a no-timestamps container+codec like mjpeg to insert gettimeofday()-based DTS/PTS ?

mjpeg is not a container

> The typical use is an IP cam, with an underpowered CPU, which is rarely reaching the announced framerate, the effective
> rate varying wildly depending on the complexity of the image.

use a container that supports VFR



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