[FFmpeg-user] ffmpeg input, output and config

Zac Harvey zachary.harvey at gmail.com
Sat Dec 8 19:31:38 CET 2012

Thanks Carl,

I'll have more time this afternoon to digest your answer, but the one thing
that immediately caught my eye was when you said:

> I should probably add that streaming mp4 in realtime (via udp or other
means) seems impossible...

Can you (or anybody else) elaborate on this some more? My understanding is
that MP4 is a container for 1 or more bitstreams. My understanding is that
you use MP4 to contain your encoded video and encoded audio streams, and
then you stream them together as MP4. Am I missing something here? Why
would it be impossible to stream MP4? Thanks again.

On Sat, Dec 8, 2012 at 1:19 PM, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:

> Zac Harvey <zachary.harvey <at> gmail.com> writes:
> > So my first question is: can ffmpeg even do this?
> While the answer is probably "yes", you did not nearly
> give enough information about the setup you are using
> to actually make this a question that can be answered
> at all.
> (Of course FFmpeg can encode to h264/mp4 with the help
> of x264, and if you are not distributing binaries, you
> can of course use libfaac to encode aac, and while I
> have never tried, user reports indicate that udp
> streaming is not unusual. Recording audio is possible
> via alsa and some alternatives, so if your system
> provides any possibility for recording audio, I guess
> you can use it from FFmpeg. The important thing that
> definitely cannot be answered is if your camera is
> supported: Not only do you need a driver afaict, the
> colour space has to be supported by FFmpeg - I suspect
> h264 cameras may not work - and in the end it may
> happen that A/V sync is impossible because alsa and
> v4l2 do not share the same timescale, you will only
> find out by trying, the v4l2 device in FFmpeg contains
> some options that may allow to correct the sync.)
> Carl Eugen
> PS: I should probably add that streaming mp4 in
> realtime (via udp or other means) seems impossible
> afair, but since this is not a limitation of FFmpeg
> (but the format), I guess this is just a typo on
> your side.
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