[streaming] Re: Streaming from raw MPEG-4

[Jeff Poole]

On Wed, November 22, 2006 4:44 pm, Nico Sabbi wrote:
> Jeff Poole wrote:
>
>>nc -l -p 3975 -u | mplayer -
>>(tell netcat to listen for udp traffic on port 3975, and then pipe that
>> to
>>mplayer which reads from stdin)
>>
>>
>
> twisted
>
>>It usually spits out a few errors until it actually detects a header (I
>>believe it's VOL headers that keep getting sent) and then it starts
>>playing the video perfectly.  But I don't know of a way to get MPlayer to
>>stream it back out.
>>
>
> mplayer udp://ip:port
>

I thought that just made mplayer read the data from UDP, not stream it
back out?  If you are trying to give me an easier way to get the data into
mplayer, I should point out that I tried that and it didn't seem to work. 
Looking at the data more, it appears that the data stream starts with a
VideoObject, containing a VideoObjectLayer...and those headers repeat
regularly, presumably to allow one to connect in the middle of a stream. 
But there is no VisualObject header, and I believe that is a problem.  I
think mplayer seeks until it finds some sort of header it can use, and
then tries to make the best of it.  But a more strict decoder would
probably look for the VisualObject header, ensure that the type is "0001"
(video), and then move from there.  Especially since the spec says you can
only repeat VideoObjectLayer headers in video, a decoder would want to see
that before it would think the stream looked valid.  At least, that's my
view -- I'm no expert.  Maybe I need to wrap this thing in a VisualObject
and maybe try to put it in an RTP stream for VLC to take in?  Would RTP be
the easiest?  Any ideas?


Jeff

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