On Mar 31, 2013, at 10:40 PM, Brad O'Hearne <[email protected]> wrote:

> On Mar 31, 2013, at 10:37 PM, Kalileo <[email protected]> wrote:
>> Being able to change the fps value on the fly might be a simpler way than to 
>> give each frame a duration. 
> 
> Can that be done? I was under the impression that time_base.den had to be set 
> up front and couldn't be changed mid-encoding. If changing the time_base.den 
> every frame is perfectly fine, and won't corrupt things, then that certainly 
> would be the way to go.


Presuming there's no unknowns about changing the time_base.den on the fly 
throughout encoding, problem solved. Throughout the weeks of Googling and 
reading endless source code, forum / mailing list posts, blogs, etc. on this, I 
had picked up the impression that time_base.den was to be set once prior to 
encoding and not mucked with thereafter. However, I just used the duration to 
calculate the frame rate and now I'm setting the time_base.den prior to pts and 
dts for every frame. Works great. 

Provided that there aren't any surprises in returning back to outputting over a 
network stream (I had changed my original need to outputting to a file for 
simpler testing), it appears I've bested this use case. I want to thank 
everyone who took time to dialog and lend their knowledge and assistance with 
my questions, it is greatly appreciated.

While it was moderately easy to get an initial body of source code together for 
solving this problem, this was a fairly difficult problem to solve. There were 
many nuances and things to figure out which never surfaced in questions I 
posted to this mailing list. Answers to questions were not easy to find -- I'm 
not sure about the history of the source code, but the examples and posts 
around the Internet seemed to present a fair number of red herrings and 
disinformation (perhaps unintended). Anyway, this is all to say that the source 
code I used to prototype this pipeline is out on Github, free for anyone else's 
reference: 

https://github.com/BigHillSoftware/QTFFmpeg

Hopefully this will help any new travelers using FFmpeg on a Mac, encoding with 
QTKit, and perhaps save them a little time down the road. 

Thanks again to everyone who helped, 

Cheers,

Brad

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