[Libav-user] ASF Muxer quality question / problem (C API)

Elliot Blackburn elliotb at sparkol.com
Fri Jun 20 11:08:46 CEST 2014

I'm creating an API for ffmpeg in C to be able to talk to an AS3 AIR
application, the AS3 is mostly just handing off basic commands at the right
time and the API and ffmpeg are doing all of the work in this instance.
Ffmpeg is just used to make our little animations into a video that someone
could send to whoever it's intended for.

When we first set it up for this small application we found that the asf
muxer gave us a low quality result file for the first 3 seconds or so, and
then it was fine whenever we tried to use our program to render a little
animation to WMV in 1080p. The first 3 seconds or so would be low quality
and quite pixelated.

So get around this at the time the last guy who set it up forced the codec
to change to WMV2 a bit further in the API code rather than using the
default output (which I think is msmpeg4v3?). However this is creating a
few problems that have cropped up which we've managed to just about get
around but we're looking to sort out the problems now we have a bit more

I'm under the impression that we probably just aren't passing the right
parameters in, none of us are really experts in ffmpeg and the guy who did
it first time just kind of fumbled his way through it and managed to get it
working. Past that we've not really got much experience with it. We've got
some time to sort things out and I've drawn the short straw of this fun
task (I've actually learned a lot already so it's not that bad).

I was wondering if anyone had any idea why we may be getting this
pixelation at the beginning of the output file and if there was something
that I may have missed that could potentially cause this problem. Any
advice or help would be much appreciated!
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