Wikipedia:Reference desk/Archives/Computing/2015 September 8

= September 8 =

Why doesn't DVD menu music loop seamlessly?
Just something I've always wondered about. DVD menus tend to feature music, and that music tends to play and then stop abruptly and repeat (can't comment on Bluray, I've never used it). Compare to videogames, which have had music that loops seamlessly since at least NES-days. Is there some technical limitation to DVD players that means seamless looping isn't an option? The alternative is that the menu-makers just can't be bothered. 129.96.85.21 (talk) 03:47, 8 September 2015 (UTC)
 * Music in videogames is specifically composed to loop endlessly. With DVD's they tend to pick up some piece from the movie that was never designed to loop at all. SteveBaker (talk) 03:58, 8 September 2015 (UTC)


 * What you are experiencing is the brief time it takes the head of the DVD player to seek to the point where the music and video starts. A DVD menu does not load it all into memory like a video game, it's simply looping a section of the DVD over and over. It has nothing to do with if the music is made to loop or not, and it has nothing to do with the piece of music selected as stated above. 217.158.236.14 (talk) 09:01, 8 September 2015 (UTC)


 * It isn't just the seek time for the DVD head. It is also encode time. Depending on the quality of the DVD player and the error correction required to read data from the disk itself, it can take a long time (in a computing sense) to start encoding the DVD data and create a video and audio signal for the television. Once started, each frame requires much less computation. That first frame - where the looping video starts - has to start from scratch. For reference, I had a Sony DVD player that didn't stutter at all when looping the menu track. It buffered the video and audio and went seamlessly around the loop. I also had a Panisonic and I believe an RCA DVD player. They both had a very noticeable pause when looping. The oldest one (the RCA) would black out the video when it hit the end of the loop and it would come back again when the loop restarted. It also blacked out between "tracks" in the movie. 209.149.115.219 (talk) 12:34, 8 September 2015 (UTC)
 * Right, but all of the above doesn't make seamless looping impossible, it just makes it more difficult. My understanding is that a DVD menu could be made to do a nice seamless loop of video and audio, at least on a nice player with plenty of buffer room. It's just that the publishers have not found that to be worth the extra time and effort. Would it allow them to sell the DVDs for more? probably not, but it would probably cost more to develop. SemanticMantis (talk) 13:48, 8 September 2015 (UTC)
 * I think it is impossible simply because the DVD-Video standard doesn't support it; compliant players are permitted to insert an audio gap and there's nothing that disc authors can do about that. I'm not certain because I've never actually seen the standard, but I know the programmability of DVDs is very limited. You can't feed waveforms or pitches to the audio chip programmatically, as you can on an NES or PC; you can only tell the player to play a pre-encoded MPEG-2 track. -- BenRG (talk) 18:44, 8 September 2015 (UTC)


 * I think the issue is separating the DVD from the DVD player. On the DVD, it is easy to set up a seamless loop. Just have the last frame be what would come directly before the first frame of the loop. When it hits the end, it repeats at the beginning. You have a seamless loop. But, that requires a DVD player to be fast enough to jump from one location on the DVD to another and keep playing without a little pause. There is no way to have a DVD make a DVD player work faster. It is a trait of the DVD player itself. So, if the DVD player is fast enough, there is no lag and you have a seamless loop. If the DVD player is not fast enough, you get a lag while it jumps to a new location and starts what is perceives as a wholly new video. 209.149.115.219 (talk) 18:54, 8 September 2015 (UTC)


 * Seamless branching is a part of the DVD-Video standard, so compliant players have to support it. They do that by pre-buffering enough of the MPEG stream to hide the seek time. So it is not true that the gap happens merely because some DVD players are too slow. They aren't allowed to be too slow. It must be that the standard doesn't support seamless looping of a menu clip, or it does but the disc authors don't flag the loop as seamless for some reason, or they do but many players don't comply with the standard.
 * This page seems to say that seamless menu looping is not supported on Blu-ray (or at least not supported by Sony's official validator as of three years ago), but I may be misinterpreting it. -- BenRG (talk) 20:54, 8 September 2015 (UTC)
 * OP here. Thanks for your explanations. So it seems to be primarily due to head seek time, and there is enough variation in hardware that some players are better than others in this respect, some buffering so that there is no noticeable skip. That seemed to mostly clear it up until BenRG raised the mystery of seamless branching, which Wikipedia claims is used in the Lion King. I wonder if many people, and especially those with cheap DVD players, are seeing a noticeable skip when electing not to watch the optional scene in the Lion King? Interesting. Anyway, good show everyone. 129.96.81.209 (talk) 08:06, 10 September 2015 (UTC)


 * Seamless branching is a red herring. It isn't used for intro loops. The issue is solely the time to restart the video. If it buffered it nicely, it could handle the restart without any break at all. Most hardware doesn't spend the money on that buffering because customers don't want to spend even an extra dollar for it. 209.149.115.219 (talk) 15:51, 10 September 2015 (UTC)

Java heap size
What is the maximum the heap can be for 64-bit Java on 64-bit Windows 10? Bubba73 You talkin' to me? 06:11, 8 September 2015 (UTC)
 * My reading of sources like    is it's probably over the maximum memory size of 512 GB for Pro/Enterprise and 128GB for non Pro so it's not likely to be a limit you'll find significant. Nil Einne (talk) 08:40, 8 September 2015 (UTC)


 * We are having trouble getting more than about 12GB bytes and don't know why. The error message is below:

The parameter 31000000000 divided by 2.25 is the number of bytes requested. Here 28 billion works (12.4 billion bytes, 11.59GiB) but 29 billion (12.89 billion bytes, 12.004GiB) or higher doesn't work. This is on 64-bit Windows 10 and 64-bit Java. The computer has 32GB installed and it says that about 28GB of physical memory is available. Bubba73 You talkin' to me? 02:31, 9 September 2015 (UTC)