[FFmpeg-devel] higher-level libs?

David McNab rebirth
Tue Nov 20 23:57:41 CET 2007


On Tue, 2007-11-20 at 01:12 -0500, Rich Felker wrote:
> >  - read a frame and:
> >      - extract the video raw data, preferably as planar YUVA 4:4:4 but
> 
> YUV 4:2:0 with no A is a lot more standard. Why would you want a
> format that's likely not to be usable as-is? And (extremely slow!!)
> resampling for no good?

To save me the hassle of upsampling to 4:4:4 when I want to apply
filters needing the higher chroma res, such as chromakey.

> >      - extract the audio raw data
> In what format? :)

Raw signed 16 or 32 bit samples preferred.

> >  - open an output file, and set the encoding options with a maximum
> >    of simple abstraction and a minimum of fuss
> >  - write a frame, give raw video and audio data
> 
> Both at the same time? Some buffering is certainly needed for a
> trivial api like you want. How to deal with that is nontrivial.

I'd be happy to read/write audio on a per-video-frame granularity.

> >  - for file formats that support it (eg DV), seek to arbitrary positions
> >    in the file
> 
> All formats support it, it's just a question of how fast they can do
> it and whether parsing the codec data is needed.. But what's meant by
> "seek to position X" requires some thought.

What I should have said is 'for formats such as DV that have uniform
sized blocks of video/audio data, such that it's possible to seek to
arbitrary positions and overwrite n frames without clobbering the
following frame.

As it is, my framework uses a popen'ed ffmpeg to convert to DV format,
then libdv (bless its simplicity) to read the frames. On render, I'm
using libdv to write the output, and optionally popen'ing ffmpeg to
transcode to desired final format if other than DV.

Not nice, I know. But it will suit for now, until (or unless) I bite the
bullet and drag my neurons kicking and screaming through the hideous
low-level complication of lavc/lavf.

Cheers
David

> 
> Rich
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