Mailing List Archive

On 31 Jul 2003, Saravanan Subbiah wrote:

> Does commercial skip work with PVR 250 with hardware encoding on ?

Yes, mine skips commercials..... but keep in mind that it will make
mistakes. I doubt that is due to the 250 though.

> Also how big will an 1 hour good quality PVR-250 encoded mpeg be in MBs

I get fairly good results all the way down to 1GB per hour. It is MPEG
1/2, compare to other MPEG content if you want to know what the quality
will look like. If you think SVCDs look good, set for that bitrate and you
will get video that pretty much looks like SVCD if you feed it a nice
clean signal. Just down't turn the bitrate/resolution down too far (VCD
for example) or you will expose the unfinished nature of the ivtv drivers.

Eventually (when the API settles, according to other posts here) we will
be able to configure different profiles and pick one on a per recording
basis. But for now, just pick a good happy medium and stick a decent
sized HDD in, they are cheap enough these days.

--
John M. http://www.beau.org/~jmorris This post is 100% M$ Free!
Geekcode 3.1:GCS C+++ UL++++$ P++ L+++ W++ w--- Y++ b++ 5+++ R tv- e* r

Can you explain in more detail what you mean by the unfinished nature of
the ivtv? Are you talking pixelation in the VCD format?

I've got one of these coming in the mail and My goal is to fit 1 hour of
video per 700MB CD, for archiving. This makes it sound like rates under
1GB per hour aren't very good with ivtv.

Does anyone else encode to VCD/SVCD with a bitrate/resolution that will
fit on one CD, with the pvr-250?

Thanks,
Brian Hayward

>I get fairly good results all the way down to 1GB per hour. It is MPEG
>1/2, compare to other MPEG content if you want to know what the quality
>will look like. If you think SVCDs look good, set for that bitrate and you
>will get video that pretty much looks like SVCD if you feed it a nice
>clean signal. Just down't turn the bitrate/resolution down too far (VCD
>for example) or you will expose the unfinished nature of the ivtv drivers.
>
>Eventually (when the API settles, according to other posts here) we will
>be able to configure different profiles and pick one on a per recording
>basis. But for now, just pick a good happy medium and stick a decent
>sized HDD in, they are cheap enough these days.
>
>

--
Brian Hayward

If you're going to archive, why not re-encode? Well, I guess there have
been re-encode problems, so hours of searching archives would be in
order. (unless someone here can summarise re-encoding glitches folks
have had)

I just picked up an athlon 2400+ for $70.00, so CPU is cheap these days
too.

On Thu, 2003-07-31 at 06:32, hayward@slothmud.org wrote:
> Can you explain in more detail what you mean by the unfinished nature of
> the ivtv? Are you talking pixelation in the VCD format?
>
> I've got one of these coming in the mail and My goal is to fit 1 hour of
> video per 700MB CD, for archiving. This makes it sound like rates under
> 1GB per hour aren't very good with ivtv.
>
> Does anyone else encode to VCD/SVCD with a bitrate/resolution that will
> fit on one CD, with the pvr-250?
>
> Thanks,
> Brian Hayward
>
> >I get fairly good results all the way down to 1GB per hour. It is MPEG
> >1/2, compare to other MPEG content if you want to know what the quality
> >will look like. If you think SVCDs look good, set for that bitrate and you
> >will get video that pretty much looks like SVCD if you feed it a nice
> >clean signal. Just down't turn the bitrate/resolution down too far (VCD
> >for example) or you will expose the unfinished nature of the ivtv drivers.
> >
> >Eventually (when the API settles, according to other posts here) we will
> >be able to configure different profiles and pick one on a per recording
> >basis. But for now, just pick a good happy medium and stick a decent
> >sized HDD in, they are cheap enough these days.
> >
> >

At 06:32 AM 7/31/2003 -0500, you wrote:
>
>Can you explain in more detail what you mean by the unfinished nature of
>the ivtv? Are you talking pixelation in the VCD format?

The ivtv driver is actively being developed, and while it works there are
still more things to do with it.


>Does anyone else encode to VCD/SVCD with a bitrate/resolution that will
>fit on one CD, with the pvr-250?

Record in high quality (mine's currently set for 2.5-3GB/hour) and then
transcode to VCD or whatever format you like. The results will be *MUCH*
better than directly recording into such a low bitrate. (since while
transcoding, you can do some fancy de-interlacing or filtering to aid in
the compression process)

To get an idea of the advantages of filtering your video first, check out
this:
http://dormcam.org/s8vsvdub.html

-WD

> > Does commercial skip work with PVR 250 with hardware encoding on ?
>
> Yes, mine skips commercials..... but keep in mind that it will make
> mistakes. I doubt that is due to the 250 though.

Commercial skip should work for all cards in Myth. The only stipulation
is that with software encoders, Myth does some detection work while it's
recording, so you can take advantage of that right away after a recording
finishes. With the hardware encoding cards, you have to wait for the
commercial flagging thread to finish before you get good commercial
skip/detection. The commercial flagging thread does a much better job
of detecting and flagging commercials than the real-time blank-frame
detection method does. The flagging thread can do more analysis of the
video to better detect commercials. Also, even though I wrote the code,
I don't run Myth with auto-skip on because the commercial detection is
still not 100% accurate.

> Eventually (when the API settles, according to other posts here) we will
> be able to configure different profiles and pick one on a per recording
> basis. But for now, just pick a good happy medium and stick a decent
> sized HDD in, they are cheap enough these days.

You can already do this on a per-recording basis, but it doesn't have much
effect on pvr-250 cards since you can't change bitrate yet. Just create a new
profile on mythfrontend's recording setup screen and then goto the Advanced
Recording Options screen for a scheduled recording. You can get to the
advanced screen by either hitting 'I' again while on the normal recording
options screen or by turning the option on in setup to always use the
advanced screen.

--

Chris

On Thu, Jul 31, 2003 at 09:21:18AM -0500, Shawn wrote:
> If you're going to archive, why not re-encode? Well, I guess there have
> been re-encode problems, so hours of searching archives would be in
> order. (unless someone here can summarise re-encoding glitches folks
> have had)

OK, I'll bite.

I am nearly finished with a patch to mythmkmovie (haven't figured out how to
hack MythTV, yet, but that's probablly next) to reencode and cut commercials
on MPEG files from the PVR-250 cards.

Brief problem summary: mencoder cannot seek correctly in VBR files (MPEG is
VBR). transcode cannot deal with both audio and video to/from mpeg (why?).
My (not so) happy medium for the short-term is to reencode video only with
mencoder, then use transcode to reencode audio and handle the cutlist.

It's a bit ugly, but the results are quite nice, with a one-hour TV show,
sans commercials, fitting in about 690MB, with _very_ few visible
differences from the full-size (4GB/hr) capture.

I posted a tome on the dev list yesterday, but got no responses, so I'm
pushing ahead with mythmkmovie, for now. It will take one new command-line
argument to enable the mpeg-specific codepath.

Russ

P.S. Not much time to hack tonight, but I expect(hope) to have a patch ready
to post over the weekend.

On Thu, 31 Jul 2003 hayward@slothmud.org wrote:

> Can you explain in more detail what you mean by the unfinished nature of
> the ivtv? Are you talking pixelation in the VCD format?

When I tried crankingthe birate down into the 1.5Mb/s and 352x240 VCD
range the picture turned into total crap. As in much worse than one would
expect from VCD.

> I've got one of these coming in the mail and My goal is to fit 1 hour of
> video per 700MB CD, for archiving. This makes it sound like rates under
> 1GB per hour aren't very good with ivtv.

If you snip the commercials a one hour TV show fit in a CD at SVCD
resolution just fine. And it looks better.

But remember, the ivtv project is young and rocking on at warp speed.
They just announced first light out of the video out plug on the PVR-350.
The card is capable of encoding VCD since it can do it under that less
capable platform that Hauppauge keeps wasting time with. :) So if you
really need VCD, be patient.

--
John M. http://www.beau.org/~jmorris This post is 100% M$ Free!
Geekcode 3.1:GCS C+++ UL++++$ P++ L+++ W++ w--- Y++ b++ 5+++ R tv- e* r

On Fri, Aug 01, 2003 at 11:41:31PM -0500, hayward@slothmud.org wrote:
>
> Russ, I'm ready to do some testing on your scripts. I have 1 hour of
> video I'd like to make into a SVCD. Do you scale the image down? (e.g.
> record full quality 720x480, then reduce the image to 480,480 SVCD??)

Currently, it uses the parameters you send to mkmovie. But, mkmovie doesn't
suport image scaling. It won't be much trouble adding args for that...

Here's how you could help me out greatly. I'm having quite a time figuring
out how to create and burn svcd/dvds. I'm sure all the info is out there, I
just haven't yet comprehended it enough to make it all work.

How do _you_ create SVCDs? Have you been able to start with an mpeg and get
a burnable svcd image? How? Have you created dvds (my actual goal)?

> How long does it take to re-encode at SVCD formats?

I have an Athlon 2400, 1GB RAM, SATA drives. I am using 720x480 res, 2000
video bitrate and 192 audio bitrate. The whole procedure (see below for
details) takes about 1:1. mencoder cranks out 45 fps, and transcode gets
about 1800 fps skipping commercials, and 250 fps encoding audio. It then
"hangs" a while (about 20 minutes) reindexing the output file (I assume).

I have sent Michael my patch today (Aug 3). I'd like to add support for
image scaling, based on your suggestion. Send me some details on what you
need, and I'll start on that. (All this kinda presumes Michael will
accept my patch in the first place...)

> >I am nearly finished with a patch to mythmkmovie (haven't figured out how to
> >hack MythTV, yet, but that's probablly next) to reencode and cut commercials
> >on MPEG files from the PVR-250 cards.
> >
> >Brief problem summary: mencoder cannot seek correctly in VBR files (MPEG is
> >VBR). transcode cannot deal with both audio and video to/from mpeg (why?).
> >My (not so) happy medium for the short-term is to reencode video only with
> >mencoder, then use transcode to reencode audio and handle the cutlist.
> >
> >It's a bit ugly, but the results are quite nice, with a one-hour TV show,
> >sans commercials, fitting in about 690MB, with _very_ few visible
> >differences from the full-size (4GB/hr) capture.
> >
> >I posted a tome on the dev list yesterday, but got no responses, so I'm
> >pushing ahead with mythmkmovie, for now. It will take one new command-line
> >argument to enable the mpeg-specific codepath.
> >
> >Russ
> >
> >P.S. Not much time to hack tonight, but I expect(hope) to have a patch ready
> >to post over the weekend.
> >