TiVo Community Forum banner
1 - 4 of 4 Posts

·
Registered
Joined
·
292 Posts
One possible explanation for these quality problems could be framerate conversion. TiVos only support video with a frame rate of 29.97fps. Some movies are actually filmed at 24fps. That means that Amazon has to use some sort of framerate conversion to make them compatible with TiVo. There are various methods for doing framerate conversion, and some work better then others. These sort of motion artifacts are actually characteristic of some of the poorer techniques.

If it is a framerate conversion problem, then it would explain why it only effects some movies as only some use the 24fps "film mode".
This is not the problem. ALL movies are shot in 24 frames per second - it's the rate film is recorded as an industry standard. ALL films are then converted to 29.97 fps - it's a process called 3:2 pulldown, and it is done all the time every day. If this was the problem, then all GhostRider DVDs would also exhibit this problem, since all DVDs are also converted to 29.97 fps (for north American NTSC anyway).
The more likely explanation for this problem is simply that the Tivo hardware can't keep up with the motion-intense bitrate of these scenes, since they are almost certainly encoded at a variable bit-rate. As the complexity of the scene increases, so does the bit rate. You will sometime see these problems in low-end DVD players for the same reason, and is likely the reason you see it in other cheap hardware.
 

·
Registered
Joined
·
292 Posts
Hmmm. Not to be sarcastic, but do you think that Tivo (or Amazon) is sent rolls of film like the ones projected in movie theatres? No - I'd bet a donut that Tivo is SENT the film in a digital format, likely the same mpeg2 files that are on the DVD you buy at the store. Does it make any sense to anyone that Studios would send raw film? If it's not raw film, it's not 24 fps - It's 29.97 NTSC. Even if Tivo does the encoding, it would all be done from a 29.97 NTSC format sent from the studio.

Also, although the images may not look complex to you, an encoder can find difficulty where the human eye cannot - many pixels may look similar, but are not. A completely white screen may in fact have each pixel as a slightly different shade, causing the bitrate to be be surprisingly large.
 

·
Registered
Joined
·
292 Posts
I think the fact that you think film-based content on DVDs has to be stored as 29.97 fps NTSC says enough about your expertise in this area. I'm glad you're not sarcastic though!
Dude, read a Wiki or something before you post again. While it's possible that a DVD is 24 fps, you don't own one, and have never watched one. It almost never happens. Name a title you own thats encoded at 24 fps. I'll wait for your response.
 

·
Registered
Joined
·
292 Posts
I think, perhaps, you need to do some reading. You seem to be confusing the encoding rate with the decoding rate.
Your information was very interesting to me. It seems that I was incorrect. Thank you for posting this information. In my work, we do it differently, but that is really irrelevant. I appreciate you posting WHY I was wrong - you (Snathanb) understand the points being made on both sides, and responded accordingly.
Cheers. I may owe you a donut.
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top