[FFmpeg-user] Aspect Ratios: DAR, SAR and Frame Size
james.darnley at gmail.com
Mon Jan 13 15:36:37 CET 2014
On 2014-01-13 15:28, Adi Shavit wrote:
> 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
> As can be seen:
> - The reported frame size is 352x240. This is an aspect ratio (AR) of
> - 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
Display Aspect Ratio and Sample Aspect Ratio. The latter is also known
as Pixel Aspect Ratio in some places. This refers at the shape of the
> 2. How many pixels are *actually* stored in each frame before any
> stretching and/or padding occurs?
You answered that yourself. The frame is 352 pixels wide and 240 pixels
> 3. Does ffmpeg only stretch or does it also pad the frame to fit the
ffmpeg will not change the shape of the video unless you tell it to.
Then it does what you told it to.
> 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?
It does this.
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