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TiVo Series 2, TiVoToGo, and inverse telecine

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Anonymous
May 5, 2005 7:30:12 AM

Archived from groups: alt.video.ptv.tivo (More info?)

I was playing around with transferring some TiVo video to DVD for later
watching. I set up GraphEdit and the associated DirectShow filters and
successfully decrypted the TiVo file to an MPEG file, which I then
transferred to Linux.

However, I'm having trouble transcoding the MPEG to DVD format. From
what I can tell, it looks like the TiVo MPEG encoder is doing 3:2
pulldown detection and removal (aka "inverse telecine"), but it doesn't
do it all the time (obviously, since the video isn't always from a film
source with 3:2 pulldown performed). I'm having trouble authoring a DVD
with audio and video synced. Is anyone else seeing this?
--
Chris Adams <cmadams@hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.
Anonymous
May 5, 2005 7:30:13 AM

Archived from groups: alt.video.ptv.tivo (More info?)

I only have experience with .ty files, but I assume that a TiVo file is
similar, but encrypted.

When I decode a .ty file to an mpeg I end up with a 480x480, 29.97 fps
mpeg. It's not exactly spec, but my dvd player can handle it. I do a
quick author and it burns and plays perfectly without any sync issues.

I think it's unlikely that the TiVo is going to do any inverse telecine
on anything. TV is broadcast at 29.97 (in NTSC land, but that should
be obvious, because we're talking about 3:2 pulldown here, which
doesn't happen in PAL land...) and

If you're watching something shot on film and completed with a neg cut,
like a feature, it will have consistent 3:2 cadence throughout.

If it's film-originated, but video-finished, like a high end TV show
(Law & Order or ER) there will be 3:2 pulldown, but the cadence will
(likely) change at every cut. It will be indeterminate during
dissolves.

When my DirecTivo grabs stuff it just takes the bitstream off the dish
as-is. While it is more efficient to store film-finished material on
DVD at 24fps and add the pulldown with hardware (saving 6 frames per
second of running time of storage) the same isn't true of broadcast TV
(you have to broadcast in real time, so there is no real advantage to
broadcasting 6 fewer frames per second, and there isn't currently a
24fps broadcast standard that I know of.)

I think it's unlikely that a SA TiVo would perform inverse telecine.
It's an inexact science at best (I used to spend hours figuring out
cadence changes by eye using a Henry on poorly duped video-finished
material) and the compression is such that an 80 gig drive provides
plenty of storage, even with the redundant frames.

My guess is that you're messing the file up somehow. Can you examine
the mpeg? If you're using windows, gspot will tell you the frame rate
and size. This should be your first clue - if it's not NTSC-like then
something is happening during the transcoding.

Can you play the mpeg you end up with?

Try grabbing something you know to be fully film-finished. Make sure
there's plenty of motion in it. Have a look at your mpeg frame by
frame (including both fields) and you will be able to tell if inverse
telecine is happening or (more likely) you're dropping frames somewhere
in the process.
Anonymous
May 5, 2005 3:17:06 PM

Archived from groups: alt.video.ptv.tivo (More info?)

(relaxification@hotmail.com) wrote in alt.video.ptv.tivo:
> While it is more efficient to store film-finished material on
> DVD at 24fps and add the pulldown with hardware (saving 6 frames per
> second of running time of storage) the same isn't true of broadcast TV
> (you have to broadcast in real time, so there is no real advantage to
> broadcasting 6 fewer frames per second, and there isn't currently a
> 24fps broadcast standard that I know of.)

ATSC has 24fps modes, although nobody is using them.

--
Jeff Rife | "One minute we were spanking each other with
| meat, and the next minute it got weird."
|
| -- Joe Hackett, "Wings"
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Anonymous
May 5, 2005 8:30:53 PM

Archived from groups: alt.video.ptv.tivo (More info?)

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In article <1115277111.089436.194480@z14g2000cwz.googlegroups.com>,
<relaxification@hotmail.com> wrote:
>I think it's unlikely that a SA TiVo would perform inverse telecine.

I can't speak for newer boxes, but I know Series 1 TiVos don't. I've ripped
hundreds of hours (at least) of video from mine and burned it to SVCD or
DVD. All of the video coming from the TiVo was 29.97 fps. Inverse 3:2
pulldown is always something I've had to do as a part of editing the video
(usually with the Avisynth Decomb plugin) on material that needed it before
reencoding and burning.

_/_
/ v \ Scott Alfter (remove the obvious to send mail)
(IIGS( http://alfter.us/ Top-posting!
\_^_/ rm -rf /bin/laden >What's the most annoying thing on Usenet?

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Anonymous
May 5, 2005 11:02:26 PM

Archived from groups: alt.video.ptv.tivo (More info?)

Once upon a time, <relaxification@hotmail.com> said:
>I only have experience with .ty files, but I assume that a TiVo file is
>similar, but encrypted.

Yep. I'm running it through GraphEdit with the DirectShow filters to
get a non-encrypted MPEG2 file.

>When I decode a .ty file to an mpeg I end up with a 480x480, 29.97 fps
>mpeg. It's not exactly spec, but my dvd player can handle it. I do a
>quick author and it burns and plays perfectly without any sync issues.

I haven't tried just taking the decrypted MPEG and putting it on DVD. I
want to cut out the commercials, chop the bars off to make an anamorphic
16:9 video, etc.

>I think it's unlikely that the TiVo is going to do any inverse telecine
>on anything. TV is broadcast at 29.97 (in NTSC land, but that should
>be obvious, because we're talking about 3:2 pulldown here, which
>doesn't happen in PAL land...) and

The MPEG encoder in the Series 2 (Broadcom BCM7040) is capable of doing
it according to the data sheet. That obivously doesn't mean TiVo is
configuring it that way, but they could (it would result in better video
compression and maybe a little better quality).

>If it's film-originated, but video-finished, like a high end TV show
>(Law & Order or ER) there will be 3:2 pulldown, but the cadence will
>(likely) change at every cut. It will be indeterminate during
>dissolves.

Not only that, but some filmed TV shows are not 100% filmed. For
example, "Babylon 5" was filed (so 24 fps), but the CGI was rendered at
30 fps for some seasons, so the 3:2 pulldown was done before CGI
compositing.

>I think it's unlikely that a SA TiVo would perform inverse telecine.
>It's an inexact science at best (I used to spend hours figuring out
>cadence changes by eye using a Henry on poorly duped video-finished
>material) and the compression is such that an 80 gig drive provides
>plenty of storage, even with the redundant frames.

20% less space is a significant savings (especially since the hardware
already supports it).

>My guess is that you're messing the file up somehow. Can you examine
>the mpeg? If you're using windows, gspot will tell you the frame rate
>and size. This should be your first clue - if it's not NTSC-like then
>something is happening during the transcoding.
>
>Can you play the mpeg you end up with?

I'm running Linux. The file plays fine in mplayer, but mplayer spits
out warnings that the frame rate is changing between 24000/1001 and
30000/1001. If I try to transcode it, the video ends up out of sync
(and gets progressively worse, which would seem to indicate a frame rate
mismatch).

The file is marked 29.97 fps, 480x480, 4:3 aspect ratio, 3500 kbps
(recorded at "High" quality).

It seems like the problem is that the video is changing frame rates and
that the programs I've tried under Linux can't handle that.

>Try grabbing something you know to be fully film-finished. Make sure
>there's plenty of motion in it. Have a look at your mpeg frame by
>frame (including both fields) and you will be able to tell if inverse
>telecine is happening or (more likely) you're dropping frames somewhere
>in the process.

I will give it a try. However, nothing is reporting that any frames are
being dropped.
--
Chris Adams <cmadams@hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.
!