Is higher then 8mbps a bad idea for DVD video bitrate???

[Neishaverse]

Usually I have not had to worry about this because my titles were always over an hour, but recently a few titles I produced were only like 45 mins or less. Naturally I encoded my video at the highest bitrate because I wasnt worried about filling the blank DVD. I used 9.4 mbps CBR (The max that DVDit PE accepts) I burned on a TDK DVD-R disc. I have not had any problems on my set top before or had any bad results from TDK in the past. Every few minutes in my video I get bad spots of blocky freezing images. The spots are random, and not always at the same spot when you play the disc a few times. A few times were during spots where almost no motion was on the screen. Also keep in mind I burn with Prassi Primo DVD. As always I burn & verify. Prassi did verify the DVD after burning with no errors.

I remember hearing this along time ago, but never gave it much thought, that using very high bit rates (over 8) especially on DVD-R can be difficult for the set-top to deal with.

Can anyone shed some light on this issue for me.

Good thing I didn't use Sonic Foundry's DVD Architect, it allows up to 9.8 mbps.

Barney

[sammie]

I had the same thing happening on my old old RCA standalone, all disks played fine on my cheapo plays everything but only lasts 6 months players (various models) I had heard in a thread many months about that some players have problems. I've cut my max bitrate (I always use VBR) back to 8200. So far this seems to have eliminated the problem, but I couldn't say for sure that exactly was it, but it seemed to help.

[SaSi]

A very high bitrate is a bad thing, equally bad to a very low bitrate.

DVD specs specify you should not fall below 2Mbps and not exceed 9.8Mbps. This is for the combined bitrate of video, audio and any other stuff like subpictures, etc.

Several standalone DVD players play streams that fall well below 2Mbps, but this is not something to bet on and in general should be avoided.

However, encoding in VBR, many posts and discussions say to set the min bitrate to 300. Add to that another 224 or 192 or 128 for the audio and you certainly are below 2Mbps. Sometimes causes problems on some players.

More easy to cause problems is a high bitrate. The DVD players have a fixed speed of reading the disk and if you exceed the 9.8 Mbps (even for a few seconds), the player may freeze the picture or the audio or both, until it can catch up with the disk reads. And that is for well behaved smart players. Some may lock-up alltogether.

I have found out that at least Tmpgenc can exceed the max bitrate setting in VBR encoding. I have encoded a film in 4.8Mbps average with 8Mbps max and the final stream had some portions with peaks well above 9Mbps. Adding to that a couple of audio streams caused Scenarist to reject the final stream as invalid.

A general rule is that for avg. quality content (or low action films), you can set the max bitrate to 7Mbps and be safe.

As for the 45min contents, the DVD can encode 1 hour of video using the max. legal bitrate. This means that if you encode 45min so that it fills the disk, you will exceed the limits.

Even if you don't care to put only 45 min on a single disk, why spend twice as much time to record it (if bitrate is too high) and risk compatibility?

Just some thoughts.

[acid512]

Now, this is probably useless information, but its free, so here goes:

I make alot of Divx DVD rips, and have quite often found even relativly low bitrate avi files to play with blocky bits in strange places ie in an almost motionless scene. My pc new and pretty fast, (click the button above if you like), so i guessed i had just set the codec incorrectly.

However, when reducing the file size by converting the audio from PCM to mp3, i found the blockyness to disappear.

I dont have a DVD writer yet, so have no idea if this is any use at all, but thought it was worth mentioning.

[Craig1394]

I found that the max I can go on my Elemental Video streams(CBR)without the final muxrate exceeding DVD spec is 8.5mbps.I use this for High quality stuff, like DV tape sources and such.Due to me being a quality freak, I really don't like going under 6mbps, unless I am dealing with old VHS tapes or something low Q like that.