[MPlayer-dev-eng] [PATCH] mencoder, B-frames, and video/audio delay

[Loren Merritt]

On Sun, 22 Jan 2006, Michael Niedermayer wrote:

> well "avctx->delay= s->low_delay ? 0 : (s->max_b_frames + 1);" is the encoder
> input to decoder output delay
>
> the delay between encoder input and encoder output (=pts difference) is
> variable and between 0 and s->max_b_frames + 1 if b frames are used or 0 if not
>
> 0 1 2 3 4 5
> I B P B P
> |  \|  \|
> |   |\  |\
> I   P B P B
>
> if the encoder can output several frames at once with no input then its delay
> can be between 0 and s->max_b_frames
>
> the difference between encoder input pts and encoder output dts / decoder
> input dts should be "avctx->delay= s->low_delay ? 0 : (s->max_b_frames + 1);"
> too

Method 0: ideally, decoder's pts = encoder's pts

-1 0 1 2 3 4 5
    I B P B P      pts
    |  \|  \|
    |   |\  |\   encode
    I   P B P B
   /   / / / /
  |  / / / /     muxer compensates for delay (subtract up to bframes+1)
  I P B P B        dts
   \ \|  \|
    | |\  |\     decode
    I B P B P      pts

...but that's not how dts is stored in avi or mp4.
Method 1: if negative timestamps aren't allowed

0 1 2 3 4 5
I B P B P         pts (encoder)
|  \|  \|
|   |\  |\      encode
I   P B P B
|  / / / /
| | | | |       muxer compensates for delay (subtract up to bframes)
I P B P B         dts
  \ \|  \|
   | |\  |\      decode
   I B P B P       pts (decoder)
  / / / / /
| | | | |       player compensates for delay (subtract 1)
I B P B P         pts (display)

--Loren Merritt