TiVo Community Forum banner
1 - 12 of 12 Posts

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #1 ·
Before this weekend I had seen 4 Unbox movies and 1 Unbox TV show: Epic Movie, Night at the Museum, The Bourne Supremacy The Bourne Identity and an episode of South Park.

I have been happy enough with the quality of them - seemed to be like about "Best" TiVo recording.

But this weekend I watched "The pursuit of Happyness" and "Ghost Rider" and I noticed something that I had not seen before. There was an annoying "lag" in some scenes were objects moved quickly. It looked kind of like the Windows mouse pointer does when you turn on "Display pointer trails", although not as severe.

The odd thing is that it wasn't in all scenes, and it mainly seemed to happen with larger objects. For example, a crowd scene in "Ghost Rider" where the spectators at a Johnny Blaze jump are all waving those big foam hands, and clapping and generally moving didn't have any effect like it at all, even though there was constant motion all across the screen. But a simple dialog scene between Cage and Mendes had it every time they moved across the screen. I took some screenshots, but can't find a USB cable to connect the camera. :)

Has anyone else seen this? Is it possible that I have never noticed this before (which seems odd), or is the quality of the videos so uneven?

This really looked awful... whether I just happened to not notice it before or not, if this was my first Unbox rental, there probably would not have been anymore.
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #4 ·
I uploaded the pictures I took, so I might as well post them. :)




And this one, where the crowd moved, but there was no "lag" effect:


So do you guys think these are encoding mistakes, or done intentionally for whatever reason?
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #7 ·
Dan203 said:
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".
I bet you are right! That is a BIG oversight for an operation like this. :down:
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #11 ·
Atomike said:
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.
You're forgetting that it's possible that Amazon receives some source material in 24fps and some in 29.97 fps, but that for some reason they have used the same way of converting them.

There was nothing particularly motion-intense about the above scenes that I took screenshots of. I have played MPEG2 material on my Series 2 that was taken directly from full-bitrate DVDs and never had a problem even with the most motion intense scenes. I seriously doubt that these lower-bitrate Unbox files would be any problem for a Series 3.
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #14 ·
Atomike said:
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.
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! :D
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #20 ·
Atomike said:
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.
Keep digging! ;)

I really have no idea why some Unbox videos have this defect and other's do not, but it doesn't seem unlikely to me that the original frame rate has something to do with it.

I'm trying to find somewhere to contact Amazon about it, but no real luck... I HATE their Unbox site.
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #22 ·
I just had this exact same quality issue with "The Live Of Others". :(

Now, an interesting and possibly significant detail: when I freeze the picture and step forward step-by-step, 3 "frames" (not sure if this is the term I should use here - don't know if it shows it frame by frame) are alright, then 2 bad "frames" with the "lag effect" showed in the pictures, then 3 good ones, then 2 bad, then 3 good, 2 bad and so on.

This leads me to believe that Dan203 was right above, with his suggestion that it has something to do with the frame rate conversion when the video file was created. I think I should ask and see if Amazon has any plans on fixing this...

Either way, be warned that "The lives of others" on Unbox have this defect.

EDIT: added the screenshots of the step-by-step forwarding here, note the 3:2 sequence. After this sequence, it started over again with 3 good ones and 2 bad and so on. Look at the wheel housing on the car, and you'll see what I mean.





 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #23 ·
OK I know I'm probably talking to deaf ears here, but has anyone else experienced this issue now, besides me and Dan203?

It is a big problem for me, I can't watch any Unbox movies anymore (TV shows seem to be fine). Could anyone rent "The lives of others" and see if they see the same thing?
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #25 ·
Huh, I guess they must have removed it as a rental.

I just tried to watch "Across the Universe" though, and it was the same thing there, though not at all as pronounced. It's for rent at $0.99 this weekend, so if you or someone else would like to rent and see if you see the same, that would be nice...
http://www.amazon.com/Across-the-Un...ie=UTF8&s=digital-video&qid=1207967560&sr=1-2

There's a scene about 4 minutes into the movie where I took these pictures. If someone could pause and do the same check and see if you get the 3:2 pattern that would be nice...




 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #29 ·
Mike:

It sounds like you think this is a 3:2 issue. I just wonder if there is a chance it could be specific to your TV model´s handling of 3:2?
If it is indeed an issue with that (which I have no idea if it is, other than the suspicions mentioned above), I must never have noticed it before. I tried all the different output modes on the TiVo, and the result was the same.

But it certainly is a possibility.
 

·
Registered
Joined
·
25,992 Posts
Discussion Starter · #34 ·
Thanks greg and flip123! Good to hear once again that I'm not alone in having this issue.

I sent a PM to TiVoStephen asking him to look at this thread, but haven't gotten a response.
 
1 - 12 of 12 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