[vlc] Re: streaming output question(s)

[Laurent Aimar]

On Wed, Feb 26, 2003, Alexis Guerin wrote:
> Hello,
Hi,

>  - It doesn't seem to be possible to send the video output both to the
> network (or file) and to screen display, or better, to the network, to
> screen display AND to a file. Is there any plan to implement that? That
> would be a great feature.
 It won't be done in the near future, but I'm think about it.
For a workaround, just start another vlc.
(You could dump raw file with this vlc, for example to dump a network stream:
 vlc udp/dump://@address --demuxdump-file <filedump>
or use stream output capabilities. )

> - What are exactly the MPEG-4 streaming features of vlc?
> On the streaming feature page of your web site, it is written MPEG PS/TS
> muxer and AVI muxer. These 3 format are available via in the interface
> for output to a file, but only the TS muxer is available for output to the
> network. So my question is : how is the MPEG-4 compressed stream muxed in
> a TS stream? 
> Is it the same as for an MPEG-2 streams? Is it a "standard" (common)  way to 
> stream MPEG-4, and is VLC the only client able to read such a stream?
 MPEG-4 is muxed in TS by the same way that mpeg2, there is just some
new descriptors(mandatory) in PMT to help the demuxer. This way is 
standardisated by the amendment 7 of the ISO/IEC 13818-1 (mpeg 2 system).
 But I don't know another player that will accecpt such stream. (If you find
one I will be interested to test interoperability.)

> - I tried to stream a file containing MPEG-4 video (DIVX) and MP3 audio (I 
> also tried the same file with AC3 audio instead of MP3 --> same result), and 
> it is worked, but the video is bad during a few seconds (during 5-10s I can 
> mostly see gray blocks on the screen) and it then come back to the normal 
> quality.
> Have someone else seen this problem or i am doing something wrong?
 No,it's all right, the decoder need a I-frame to produce correct video. But
MPEG4 I-frame is emited rarely compared to mpeg2 (as I-frame needs a lot of
bits to be encoded compared with P-frame), thus producing bad video for a 
few seconds.
 The only way to avoid that, is to encode your video with more I-frames,
(but required a higher bitrate).

> - A last question is about transcoding. Does anyone know if it is possible to 
> make VLC use stdin as an input?
 Yes, use "-" as input file name.
cat file.mpg | vlc -
will play file.mpg. Works well with mpeg/ogg/asf file, will work only with a
few avi.

> What I want want to do is to send the output 
> of transcode or mencoder to vlc. but it might actually not even be possible
> to send the output of mencoder on stdin... any comments?
 See their documentation, or you could use name fifo (man mkfifo ;).

> Thanks for your comments,
> And thanks for this great software!! These new streaming output capabilities 
> are very interesting, especially the divx streaming one.
 Thanks :)

-- 
fenrir

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