[FFmpeg-user] Aspect Ratios: DAR, SAR and Frame Size

[Adi Shavit]

Hi,

  I have a video for which ffmpeg -i prints: Stream #0:0: Video: vp8,
yuv420p, 352x240, SAR 10:11 DAR 4:3, 15 fps, 15 tbr, 1k tbn, 1k tbc
(default)

As can be seen:

   - The reported frame size is 352x240. This is an aspect ratio (AR) of
   22:15
   - SAR = 10:11
   - DAR = 4:3

I have a few questions about these AR values:


   1. Obviously, the frame size is the decoded size of the frame.
   However, what do DAR and SAR mean in this context when they are both not
   1:1?
   2. How many pixels are *actually* stored in each frame before any
   stretching and/or padding occurs?
   3. Does ffmpeg only stretch or does it also pad the frame to fit the
   output?
   4. My usage does not care about the displayed video aspect-ratio, but I
   would *really *like to avoid any padding and also reduce any unnecessary
   processing (like stretching/scaling).
   Is it possible to tell ffmpeg to do decode the frames/pixels while
   keeping their internal AR and avoiding any padding and/or stretching?


Thank you and warm regards,
Adi