Ask questions to BD authoring and compression insider "2themax"

[Icemage]

Originally Posted by 2themax

Yes that does take into account room for opening logos and menus, but not all that much. The idea on titles this long would be to give every available bit on the disc to the feature.

There is a slightly higher peak for Dolby TrueHD over DTS-MA. That's also factoring in core audios for both. From what I've observed, it's usually a small difference though. Dolby TrueHD may spike 500-600kbps higher than DTS-MA. When you have the bandwidth that we do on Blu-ray, it's hardly a factor.

I see! Much thanks for the clarification. I've learned something new today!

The most recent test I do was on a music title. The PCM was at 5.1 24bit/48kHz, which peaks at 6.912Mbps. The peaks for Dolby TrueHD and DTS-MA were roughly 6.1Mbps and 5.6Mbps respectively. With any one of the 3 audio bitrates, the video would still be peaking at 40Mbps. It would, however, affect the ABR of the video slightly.

Can you expand more on what the different effects on video ABR would be?

The way I've been led to believe, as long as the total audio streams total less than 8Mbps, then the 40Mbps peak is safe in all instances if we're just talking about bandwidth usage and had infinite storage capacity.

How, then, does the video ABR decrease based on the audio codec used in this example? Is it because of capacity issues (i.e. PCM 5.1 24/48 eats up a lot more space, and therefore less capacity can be allocated, making the max sustainable ABR lower?).

Is there a piece of the puzzle that I'm missing somewhere, or is the video ABR difference you mentioned above simply due to storage capacity limitation changes based on the space consumed by the audio?