Blu-ray's bitrate limit

[Chengbin]

The blu-ray specs say a video cannot exceed a bitrate over 40mbits. Does that apply to overall bitrate or that's the highest bitrate you can have in any part of the video? If it is the latter, wouldn't the high motion scenes look terrible?

[LoRd_MuldeR]

This is from Wiki:
BD Video movies have a maximum data transfer rate of 54 Mbit/s, a maximum AV bitrate of 48 Mbit/s (for both audio and video data), and a maximum video bitrate of 40 Mbit/s.

However the maximum (local) bitrate of the video is limited by the VBV constraints, I think. MeGUI uses a Maximum VBV bitrate of 38.000 and a buffer size of 30.000 for BD.

[SeeMoreDigital]

So does this mean... no video "peaks" above 40Mbps either?

[Manao]

It can go above 40 mbps if the peak is short enough. With 40/30 as maxrate/vbvsize, you can reach 70mbps over one second. Anyway, 40 mbps is enough for 1080p24.

[LoRd_MuldeR]

As far as I understand, the "Maximum VBV Bitrate" is the maximum bitrate to fill the buffer with new data. Not the maximum (local) video bitrate!

If the video bitrate exceeds the maximum VBV bitrate (which is allowed), then the buffer will start to run out of data.

Therefore the bitrate spike can only be short. Otherwise that would cause a buffer underrun, a VBV violation - the authoring software would reject such streams.

[rack04]

There is a scene in POTC2 at about 35 minutes where the video bitrate reaches 49.5Mbps and audio bitrate at 6.9Mbps.

[Chengbin]

There is a scene in POTC2 at about 35 minutes where the video bitrate reaches 49.5Mbps and audio bitrate at 6.9Mbps.

I just did that with Kung Fu Panda (mainly because it is really short, like 17GB). The maximum video bitrate is 36mbps. I'm too lazy to do it with other disks since you just proved it.

[benwaggoner]

There is a scene in POTC2 at about 35 minutes where the video bitrate reaches 49.5Mbps and audio bitrate at 6.9Mbps.
Measured by the bitrate meter in the player, or an analysis tool?

Because the player bitrate meters are pretty notoriously inaccurate.

[Chengbin]

I used bitrate viewer, I think that's pretty accurate.

There is a bitrate meter in a Blu-ray player??? Seems like a really useless function.

[rack04]

Measured by the bitrate meter in the player, or an analysis tool?

Because the player bitrate meters are pretty notoriously inaccurate.

Measured by the player.

[Gokumon]

There is a bitrate meter in a Blu-ray player??? Seems like a really useless function.

What's so amazing about that? DVD players have them too.

[LoRd_MuldeR]

DVD players have them too.

Confirmed.

[Chengbin]

I've never seen or even heard of that feature. Wow. I learned something new today.

[rack04]

I've never seen or even heard of that feature. Wow. I learned something new today.

Not my pic but it will show you what I'm talking about.

http://i11.photobucket.com/albums/a199/rack04/495mbps.jpg

[Comatose]

I used bitrate viewer, I think that's pretty accurate.
I was told it doesn't take VBV limits into consideration.

For that you'll have to use neuron2's VBVChecker or Elecard StreamEye.

[benwaggoner]

I was told it doesn't take VBV limits into consideration.

For that you'll have to use neuron2's VBVChecker or Elecard StreamEye.
Exactly. Useful numbers require a good analysis tool.

The DVD/BD meters tend to report momentary total mux rate, not the current video ABR accounting for VBV, which is harder to calculate during playback than you might think. And if there's any VBR audio, it's really hard to figure out even a ballpark of the real peak bitrate.