Max + average bit rates advice

[insch]

What is best practice on setting max + average bit rates on BD encodes in Toast? Default seems to be max = 16 Mbps and average = 8 Mbps. What would give me the best picture quality along with widest playability?

Thank you.

[Ryu77]

Originally Posted by insch

What is best practice on setting max + average bit rates on BD encodes in Toast? Default seems to be max = 16 Mbps and average = 8 Mbps. What would give me the best picture quality along with widest playability?

Thank you.

I have never used Toast. However, Having a max bitrate of 16 Mbit/s would ensure AVCHD compliancy also. If you are only going to be using BD Media then you can safely push max bitrate to 45 Mbit/s.

Average bitrate would be dependent on the duration of the video you wish to encode vs. the available space on your media. Don't forget to allow extra room for the M2TS headers. These are quite large as M2TS is a Transport Stream and a lot of extra space is dedicated to error prevention. Some basic guidelines for you...

H264 Video Stream: 5%
Dolby Digital Audio: 17.5%
DTS Audio: 16.6%
Dolby TrueHD Audio: 30% - 45% (Yes, this much extra room is required!!)
DTS-HD MA: 10% - 12%

Note: HD audio tracks are variable bitrate so you will need to multiplex them into a M2TS container to calculate file size overheads each time.

So, you will need to allow the above percentages on top of the file size. For example if you have a Dolby Digital track that is 650 MB, and you multiply that by 1.175, the result is 764 MB. You will need to allow 764 MB For your audio track. If you are using a BD-25 for your project, you would subtract 764 MB from 23,866 MB (usable space on a single layer Blu-ray disc) and then multilpy the answer by 95% (for the H264 header space).

23,866 - 764 = 23,102
23,102 x 0.95 = 21,946

Using a bitrate calculator, if the video was 2 hours in length, you could use an average video bitrate of 25,565 Kbit/s.

Hope this helps. If you have more questions, please ask.

[insch]

Thank you - that's really helpful. This film is 42 mins in length - currently with just a stereo soundtrack (I was planing to use PCM) but I will be adding a DTS 5.1 encode later. Your bit rates seem high (but I'm not complaining!) The highest bit rate I can set on Toast is 26 Mbps so I guess that would be ok with an average around 23 or 24?

Best.