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It would be nice to have a board which could take input from an internal frame buffer of sorts, rather than only from an external analogue input. This would allow for easy generation from arbitrary sources.

Likewise a decoder which could decode to memory would be useful (although it seems that the DVB cards must be able to do something similar because you can attach xawtv to the /dev/video device without incuring cpu overhead... It seems to be quite easy to stream an mpeg to be decoded to a H+ card, or the DVB card, and presumably will be for the PVR350 card - the trick is how to mux in an overlay stream for on screen menus and display (but if anyone is keen I think there is sample code to do exactly this in the H+ plugin for vdr)


-----Original Message-----
From: Alberto Grazi [mailto:alberto.grazi@db.com]
Sent: 25 April 2003 10:29
To: mythtv-users@snowman.net
Subject: [mythtv-users] New MPEG2-Encoder board available


Sounds good news, doesn't it ?

http://linuxtv.org/news/ml/mpex.xml
http://linuxtv.org/mpeg2/mpex.xml




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Edward Wildgoose wrote:

>It seems to be quite easy to stream an mpeg to be decoded to a H+ card, or the DVB card, and presumably will be for the PVR350 card - the trick is how to mux in an overlay stream for on screen menus and display (but if anyone is keen I think there is sample code to do exactly this in the H+ plugin for vdr)
>
If you're talking about the full DVB cards, from what I understood, you
can tell them what to do with the data via the demux devices. You can
tell them to accept an MPEG stream from either the tuner or from the app
(via dvr device), demux it and to output to the MPEG decoder or the app
(dvr device). So, you can tell them to decode an MPEG stream on the disk
and presumably get it decoded from /dev/video or tvout. There are also
special provisions to create OSDs, but I didn't look into that.

> If you're talking about the full DVB cards, from what I understood, you
> can tell them what to do with the data via the demux devices. You can
> tell them to accept an MPEG stream from either the tuner or from the app
> (via dvr device), demux it and to output to the MPEG decoder or the app
> (dvr device). So, you can tell them to decode an MPEG stream on the disk
> and presumably get it decoded from /dev/video or tvout.

I'm not sure if they can get it from the disk themselves, but certainly I think all you need is to tweak a register and then feed the data in and it comes out on /dev/video as a v4l 1 or 2 device (you can have either)

> There are also
> special provisions to create OSDs, but I didn't look into that.

Yeah, but see the VDR list. Everyone is trying to work out how to get around this because they are pretty limited. Basic ascii. You don't get the eyecandy that you get with myth. However, some way of doing a basic mux of the eye candy encoded as mpeg 2 together with the mpeg2 stream should fix that.

I think that this is what the H+ plugin for vdr does. It has a requirement for ffmpeg and I wonder if this is what they are using to generate and mux the extra graphics in...

..Aha, just checked. My mistake I think the relevant stuff appears to be in spuenc.c and the header says:

* spuenc.c - encodes an OSD bitmap as subpicture
*
* Assimilated and adapted by
* Stefan Schluenss <dxr3_osd@schluenss.de>
* Nov. 2002
*
* Based on the subpicture encoding routines from MPlayer and
* the information given by
* Samuel Hocevar
* Michel Lespinasse
* and http://members.aol.com/mpucoder/DVD/spu.html