Mailing List Archive: MythTV: Users

MythTV Transcode Proxy

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chasedouglas.lists at gmail

Feb 15, 2009, 9:18 AM

Post #1 of 7 (1363 views)
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MythTV Transcode Proxy

Hello all,

I wanted to mention a project I've been working on call MythTV
Transcode Proxy, or MTP. It allows for a slightly modified frontend to
connect to a mythtv setup from across the internet, even if there are
multiple slave backends and the system sits behind a NAT router. All
control messages (and video streams if you want) are encrypted using
TLS-SRP. Finally, and this is most interesting to me, the frontend can
request the stream to be transcoded on the fly to a format of the
frontend's choosing.

More details can be found at http://trac.assembla.com/legend/wiki/MythTVTranscodeProxy
.

I would enjoy hearing of any and all comments, questions, and concerns
anyone may have. My intention is that this can be used to allow for
all kinds of atypical frontends, such as frontends on mobile devices.
I am also currently working on an iPhone frontend, but it is very far
from completion. However, I can attest that it can play back video
streams from my backend to my iPhone on AT&T's 3G network.

Thanks,
Chase Douglas

P.S.: I find Qt to be marvelous, but c++ itself to be clumsy (when
compared to objective-c at least), so if anyone peeks at the code and
sees any code misuse or design flaws, I'm all ears.
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derliebegott at gmail

Feb 16, 2009, 4:04 AM

Post #2 of 7 (1294 views)
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Re: MythTV Transcode Proxy [In reply to]

2009/2/15 Chase Douglas <chasedouglas.lists [at] gmail>:
> Hello all,
>
> I wanted to mention a project I've been working on call MythTV Transcode
> Proxy, or MTP. It allows for a slightly modified frontend to connect to a
> mythtv setup from across the internet, even if there are multiple slave
> backends and the system sits behind a NAT router. All control messages (and
> video streams if you want) are encrypted using TLS-SRP. Finally, and this is
> most interesting to me, the frontend can request the stream to be transcoded
> on the fly to a format of the frontend's choosing.
>
> More details can be found at
> http://trac.assembla.com/legend/wiki/MythTVTranscodeProxy.
>
> I would enjoy hearing of any and all comments, questions, and concerns
> anyone may have. My intention is that this can be used to allow for all
> kinds of atypical frontends, such as frontends on mobile devices. I am also
> currently working on an iPhone frontend, but it is very far from completion.
> However, I can attest that it can play back video streams from my backend to
> my iPhone on AT&T's 3G network.
>
> Thanks,
> Chase Douglas
>
> P.S.: I find Qt to be marvelous, but c++ itself to be clumsy (when compared
> to objective-c at least), so if anyone peeks at the code and sees any code
> misuse or design flaws, I'm all ears.

Hi,

this sounds absolutely great even for typical frontends. or for my PocketPC.

> the frontend can request the stream to be transcoded
> on the fly to a format of the frontend's choosing.

This feature is something I really need, because one of my frontends
it an old slow notebook and it would be great to be able to request a
recording with a smaller resolution or bitrate => I do not need 720p
on a old CRT TV.

As I see it supports only LiveTV at the moment and recordings will
come later. 0.22 should (I read somewhere on the list) handle
MythVideo files like normal recordings (stream them through backend)
and MTP could maybe handle even these files.

But ... how much "power" does the backend/proxy need to transcode on
the fly?! Could VDPAU be used for transcoding?!
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mythtv-users2 at dwilga-linux1

Feb 16, 2009, 6:34 AM

Post #3 of 7 (1298 views)
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Re: MythTV Transcode Proxy [In reply to]

At 12:18 PM -0500 2/15/09, Chase Douglas wrote:
>Hello all,
>
>I wanted to mention a project I've been working on call MythTV
>Transcode Proxy, or MTP. It allows for a slightly modified frontend
>to connect to a mythtv setup from across the internet,

Very cool idea. Please update the list when you get recordings to stream.
--
Dan Wilga "Ook."
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eric at lisaneric

Feb 16, 2009, 2:08 PM

Post #4 of 7 (1295 views)
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Re: MythTV Transcode Proxy [In reply to]

On Sun, Feb 15, 2009 at 12:18 PM, Chase Douglas
<chasedouglas.lists [at] gmail> wrote:
> Finally, and this is
> most interesting to me, the frontend can request the stream to be transcoded
> on the fly to a format of the frontend's choosing.

I've been thinking about something like this for a while now with
respect to the mvpmc project (http://mvpmc.sourceforge.net). They
support on-the-fly transcoding through vlc, but it doesn't really work
very well for mythtv recordings.

It would also be really nice in a house with some HD and some SD
frontends in different rooms to be able to transcode an HD recording
into SD for playback on a low-end frontend system.

Ideally, I'd think this would be something that could be integrated
into the backend/frontend protocol itself, rather than being a
separate piece.

Eric Sharkey
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stuart at xnet

Feb 16, 2009, 3:06 PM

Post #5 of 7 (1283 views)
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Re: MythTV Transcode Proxy [In reply to]

Chase Douglas wrote:
> Hello all,
>
> I wanted to mention a project I've been working on call MythTV Transcode
> Proxy, or MTP. It allows for a slightly modified frontend to connect to
> a mythtv setup from across the internet, even if there are multiple
> slave backends and the system sits behind a NAT router. All control
> messages (and video streams if you want) are encrypted using TLS-SRP.
> Finally, and this is most interesting to me, the frontend can request
> the stream to be transcoded on the fly to a format of the frontend's
> choosing.
>
> More details can be found at
> http://trac.assembla.com/legend/wiki/MythTVTranscodeProxy.
>
> I would enjoy hearing of any and all comments, questions, and concerns
> anyone may have. My intention is that this can be used to allow for all
> kinds of atypical frontends, such as frontends on mobile devices. I am
> also currently working on an iPhone frontend, but it is very far from
> completion. However, I can attest that it can play back video streams
> from my backend to my iPhone on AT&T's 3G network.
>
> Thanks,
> Chase Douglas
>
> P.S.: I find Qt to be marvelous, but c++ itself to be clumsy (when
> compared to objective-c at least), so if anyone peeks at the code and
> sees any code misuse or design flaws, I'm all ears.

This is rather interesting. I think a lot of people will be interested
for different reasons. I am interested because the only thin client
that speaks native myth protocol can only handle Standard Definition /
Stereo Audio (see the mvpmc.org project). This is fine for NTSC
recordings but falls apart for ATSC recordings of any type (SD or HD).

Up to now people have been using VLC in conjunction with mythtv systems
in an elaborate linking / mounting / scripting exorcise. If this plugin
works, I can see shows being offered up to these boxes in a seamless
fashion. Excellent!

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chasedouglas.lists at gmail

Feb 16, 2009, 3:17 PM

Post #6 of 7 (1285 views)
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Re: MythTV Transcode Proxy [In reply to]

On Feb 16, 2009, at 5:08 PM, Eric Sharkey wrote:
> On Sun, Feb 15, 2009 at 12:18 PM, Chase Douglas
> <chasedouglas.lists [at] gmail> wrote:
>> Finally, and this is
>> most interesting to me, the frontend can request the stream to be
>> transcoded
>> on the fly to a format of the frontend's choosing.
>
> I've been thinking about something like this for a while now with
> respect to the mvpmc project (http://mvpmc.sourceforge.net). They
> support on-the-fly transcoding through vlc, but it doesn't really work
> very well for mythtv recordings.

In fact, I have been also been using libcmyth from the mvpmc project
for my iPhone frontend. Shortly, I'll put my changes up on my git repo
so others may be able to use them.

> It would also be really nice in a house with some HD and some SD
> frontends in different rooms to be able to transcode an HD recording
> into SD for playback on a low-end frontend system.
>
> Ideally, I'd think this would be something that could be integrated
> into the backend/frontend protocol itself, rather than being a
> separate piece.

There are a few reasons why I did not add this to mythbackend (it is
actually integrated into the protocol, there's no way around that):

1. Time taken in integrating into mythtv (I don't know my way around
it personally), time taken to get it merged into trunk, and time taken
to wait for trunk to become the next stable release.
2. Mythtv is really good for a secure network. Exposing any part of it
to an insecure network may be better suited to an external "piggy
back" solution. This is just like tunneling unsecure programs over ssh.
3. When you have multiple slave backends, the master backend would
then need to start streaming slave backend recordings on their behalf.
This is possible of course, but doesn't seem the most elegant in the
mythtv ecosystem.
4. Mythtv incorporates a certain revision of ffmpeg libraries at any
given time for all transcoding. Some users may want to transcode using
vlc, ffmpeg binaries, or mencoder instead due to codec/format support
or other issues.

However, mythfrontend could be modified to support the proxy. I don't
really have an interest in doing it if people aren't interested/won't
merge into trunk though.
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eric at lisaneric

Feb 16, 2009, 4:04 PM

Post #7 of 7 (1282 views)
Permalink

Re: MythTV Transcode Proxy [In reply to]

On Mon, Feb 16, 2009 at 6:17 PM, Chase Douglas
<chasedouglas.lists [at] gmail> wrote:
>> Ideally, I'd think this would be something that could be integrated
>> into the backend/frontend protocol itself, rather than being a
>> separate piece.
>
> There are a few reasons why I did not add this to mythbackend (it is
> actually integrated into the protocol, there's no way around that):

I didn't mean to sound critical of your approach. It looks like
you're just starting out and doing it as a standalone proxy does
simplify the integration issue.

This is the type of thing which could be folded in to the backend well
after the project has matured some more and become stable. There's no
need to rush the integration.

Eric
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