Maximum Bitrate

[unity2]

I've read that the maximum bitrate for video on a DVD is 9.8 Mb/s. But I've seen commercial DVD's that are way above that. What's the actual limit?

[Soopafresh]

Maybe HD DVDs. Standard DVD players will choke above 9.8

[redwudz]

Also, if you look to the upper left on this page for 'WHAT IS' DVD, it shows the specification of the DVD format. True, you could go above 9.8Mbps, but you risk it not playing back on some players. And the difference in quality between 9.8Mbps and say, 10.8Mbps, isn't worth the risk as you will gain little or no quality. And commercial discs are pressed with a die, not burned with a laser. This could explain any difference in bitrates.

And welcome to our forums.

[manono]

But I've seen commercial DVD's that are way above that.

No you haven't. The max, everything included (video, audio, subs, overhead) is 10.08Mbps, and most retail DVDs don't approach that. The video max is 9.8Mbps (if the other stuff added in keeps it below 10.08), and very few retail DVDs come close to that. The highest video bitrate alone you're likely to see is just above 9Mbps.

[dannymoe]

What about using DVD's to burn HD on for play back on a bluray player? Is there a maximum bit rate for that? I ask because I recently split a full Bluray into 4 smaller peices and burnt them to DVD for playback on a bluray player but it didnt work very well, the video judders to the point where it is unwatchable

[poisondeathray]

It varies by player, but <15Mb/s should play on most blu-ray players for DVD5/9 media (for those that support HD content on DVD media playback - many do not, or require special firmware to do so) . I've seen some players that can play more than that 17-21Mb/s even without stutter.

the 15Mb/s mentioned above is the maxrate - so that isn't the maximum instantaneous bitrate, it's the vbv-maxrate - which is the maximum bitrate that data can enter the buffer. This is partially dependent on rotational speeds, transfer speeds of the player

[dannymoe]

Thanks poisondeathray- I did see that the bit rate was going up to 35/mbps, but on average 15-25/mbps, I guess I have to bite the bullet and invest in blank BR discs and a burner

[edDV]

I've read of some people having trouble playing 24 Mb/s AVCHD (VBR) or 25Mb/s HDV (CBR) from DVDR media with early Blu-Ray players. It seems the original "AVCHD" DVD disc standard was ~16 Mb/s or ~2x DVD speed.

Later Blu-Ray players accommodate 24 Mb/s VBR with no problem. The DVDR disc needs to rotate faster at those rates. BD disc limits go up to 54 Mb/s (40 Mb/s ave for video) at lower disc rotational speed.

Someday I will make a test DVDR to test upper bit rate limits for my Blu-Ray players.

[Blueknight]

Maybe HD DVDs. Standard DVD players will choke above 9.8

Choke as in it shakes on the side?

[edDV]

Maybe HD DVDs. Standard DVD players will choke above 9.8

Choke as in it shakes on the side?

No, just stops leaving you flail and worry.

[andrewjameshoward]

Hope no-one minds if I jump on this thread to seek advice about bitrate - a search on the topic brought me here. I understand bitrate to be a data rate for an audiovideo stream. I also understand that when converting between formats, you can use a bitrate calculator to choose an appropriate bitrate for a given file size (which, incidentally is what I was doing when I came up with this question - converting mpg to mp4 with ffmpeg/Avanti).

But I don't have a FEEL for what is a high and a low bitrate. With mp3 audio, I know that 128 is reasonably good music quality, 64 is not but is bearable, 320 is very good quality. I also know that different compression techniques affect the space taken up by the music - eg that a (lossless) FLAC compression takes up not much more space as a (slightly lossy) mp3 at 320 whilst a (lossless) WMV is twice as large. But what are the bitrates for the FLAC and WMV? Does bitrate reflect compression method as well as quality.

Moving on to video, I have little or no feel for what constitutes high and low quality. I can see from this thread that 10Mbps is very good quality DVD. But what sizes of bitrate would be not so good, not very good, awful and unrecognisable? Also how would compression relate to this - if I had a raw video AVI (ie uncompressed video) with a 10Mps bitrate, would that be much poorer quality than a 10mpbs DVD, reflecting the compression effect? And if I know the bitrate of my incoming mpg file, what would be the relationship with the bitrate of the outgoing mp4 to give the same quality (assuming similar frame rate, screen size)?

Sorry if I've asked in the wrong place but i couldn't find this elsewhere.

[SLK001]

This is how the MAXIMUM bitrate is determined:

All DVDs are read by a DVD Spec compliant player at a constant rate of 26.16 Mbps. After a 16/8 decoding, this results in a data bitrate of 13.08 Mbps. Subtract 2 Mbps of error correction, and 1 Mbps of navigational overhead and you have a data stream that YOU can use of 10.08 Mbps. Of this 10.08 Mbps, the MAX that can be video is 9.8 Mbps (by specification). Therefore, whether you have a DVD that is encoded at 2.8 Mbps or have a Superbit DVD, it is read by the player at a constant rate of 26.16 Mbps.

Now some machines may have issues performing error corrections for high bitrate DVDs that have many errors (such as DVD+/-Rs), since this correction can be CPU intensive. But for a commercially pressed DVD, these errors are relatively low, so virtually all players can perform any needed error corrections at full speed.

So, 9.8 Mbps is your maximum rate for your video.

[jagabo]

So, 9.8 Mbps is your maximum rate for your video.

One thing that's never been clear to me is over what period of time that is measured. Is it per frame? For example, is each frame of a GOP in a 30 fps video limited to 1/30 of that 9.8 MB's, or ~0.327 Mbits? That would be a severe restriction on the I frame of a GOP. Is it the entire GOP that's limited to 9.8 MB/s, ie, a 15 frame GOP in a 30 fps video can be no more than 4.9 Mb? Or is it literally per second? For example, if one second if video is made of two 15 frame GOPs can one GOP be 9 Mb and the other 0.8 Mb?

[Bonie81]

all standard DVD players i have came across choke above 9.8 mbps, only one or two played upto 12.0 mbps and choked above that.

[poisondeathray]

So, 9.8 Mbps is your maximum rate for your video.

One thing that's never been clear to me is over what period of time that is measured. Is it per frame? For example, is each frame of a GOP in a 30 fps video limited to 1/30 of that 9.8 MB's, or ~0.327 Mbits? That would be a severe restriction on the I frame of a GOP. Is it the entire GOP that's limited to 9.8 MB/s, ie, a 15 frame GOP in a 30 fps video can be no more than 4.9 Mb? Or is it literally per second? For example, if one second if video is made of two 15 frame GOPs can one GOP be 9 Mb and the other 0.8 Mb?

It's usually expressed in seconds, but it's relative to the local buffer.

In VBR encoding, DVD compliant MPEG2 encoders use VBV model, so "maximum rate" doesn't refer to 'maximum instantaneous bitrate per unit time' , it refers to the bitrate at which data enters the buffer per unit time (usually in seconds , to "refill" the buffer.)

Restriction occurs if/when there is a buffer underflow, so it depends on the relationship of current buffer, maxrate (data entering the buffer) and output level (requested decoded data exiting the buffer for display). It's an input/output equation. DVD muxers perform this calculation based on DVD specs and will reject if the video stream result in buffer underflow. So the maximum instantaneous bitrate can actually go above that value, because of the buffer.

The official specs state that all DVD players must sustain 9.8Mbit/s video decode rate (this would imply CBR), but I used to have 2 different cheap noname brand dvd players (from China) that choked ~8.5 Mb/s

[SLK001]

The official specs state that all DVD players must sustain 9.8Mbit/s video decode rate (this would imply CBR), but I used to have 2 different cheap noname brand dvd players (from China) that choked ~8.5 Mb/s

Your cheap no name brand DVD players are probably giving you a lot of read errors that they cannot correct fast enough. To be able to even read a DVD with an average bitrate of 1.5Mbps or 9.8Mbps, the player still has to read the data off the disc at 26.16Mbps - this is the CONSTANT read rate of the raw data.

Also, the data rate might be able to peak above 9.8Mbps, provided that the buffer doesn't get drained. If it does exceed 9.8Mbps, then it won't be able to peak again until the buffer recovers substantially. And don't trust the bitrates displayed by the player - more often than not, the value displayed is not accurate. Use an off-line bitrate viewer (I use Bitrate Viewer) to get an accurate reading (and I've never seen a bitrate exceed spec using this program, but my DVD player is more than happy to display values above 9.8).

[jagabo]

I've never seen a bitrate exceed spec using this program

I'm looking at a commercial DVD VOB file right now with Bitrate Viewer. In "second" mode it shows a peak bitrate of 8876 kbps. In "GOP enhanced" mode it shows a peak of 10110 kbps. In "GOP" mode it shows a peak of 26251 kbps.

[jagabo]

It's usually expressed in seconds, but it's relative to the local buffer.

Then the peak bitrate varies with the size of the buffer and the width of the peak.