Main Concept AAC/AVC bitrate issue... at DVinfo.net

James Binder · August 23rd, 2010, 01:26 PM

Trying to render out to Main Concept AAC/AVC (mpeg4 - h264) with a constant bitrate = 5,000,000 bps

When I type that bitrate in, it won't stay selected. when I close out and come back, the bitrate (render settings) have changed to 192,000. The drop down menu only lets you select (in that range) 4,000,000 and 10,000,000 -- not 5,000,000

Anybody know why I cannot type in 5,000,000 bps and have it remain and render that bit rate?

Thanks --

Arkady Bolotin · August 24th, 2010, 11:20 AM

It is so, because the MainConcept AAC/AVC encoder included into the Vegas 9 has only two profiles to choose – Baseline (BP) and Main (MP).

At the level 2.1 (which is the specified set of constraints indicating a degree of required decoder performance for a profile), both BP and MP provide only four Mbit/s for video bit rate.

What you need is the High profile (HiP) that delivers 5 Mbit/s at the same 2.1 level. Unfortunately, HiP is missing in the Vegas 9 AAC/AVC encoder.

James Binder · August 25th, 2010, 06:11 AM

Thanks Arkady --

So to get this straight -- there is no way to output a 5mbps AAC/AVC h264 file? I'm almost certian that in Vegas 8 I could choose that option.

This seems strange to me in that this is a pretty basic setting for encoding files to be uploaded to Vimeo and the likes...

Can anyone else confirm that this WAS an option in Vegas 8?

Arkady Bolotin · August 25th, 2010, 07:07 AM

Actually, there is.

Instead of the constant bit rate = 5 Mbit/s, pick the variable bit rate: type the number 5,000,000 in the Maximum (bps) and Average (bps) fields.

Not only will this option hold easy high- and low-motion changes in your video, but it will also be able to produce higher picture quality than the constant bit rate option.

James Binder · October 4th, 2010, 07:02 AM

Thanks again Arkady.

Thought I'd bring this one back.

I've been trying this with my exports (headed to Vimeo in specific) and all seems well so far. I am curious to know if this method (by the numbers, under the hood) is providing as good as or superior results compared with the same bit rate CBR? If so (and for the tech inclined here) -- why?

By selecting the same min and max number, is one in fact creating CBR -- without any bitrate fluctuation?

I know I was able to select 5 mbits CBR in Vegas 8. Why not in ver 9?

Thanks --

Arkady Bolotin · October 4th, 2010, 04:42 PM

Hi James:

The main advantage of VBR encoding is that it produces a better quality-to-space ratio compared to a CBR encoded file of the same data. The bits available are used more flexibly in order to encode video, with fewer bits used in less demanding passages and more bits used in difficult-to-encode passages.

Suppose we have chosen the rate (at which a codec's output data should be consumed) to be constant and equal to 5 Mbit/s.

Then it might happen that we had not allocated enough data for a complex scene in our video and as a result we would get an increased blockiness in this scene, because the frames would no longer being fully detailed in their rendering.

Sure, that problem could be easily solved by choosing a high bitrate (say 25 Mbit/s). However, such a solution would inevitably enlarge the size of the resultant video file and – what’s more important – could introduce stutter when streaming the file.

August 23rd, 2010, 01:26 PM	#1
James Binder Major Player Join Date: Jan 2005 Location: NY, NYC Posts: 367	Main Concept AAC/AVC bitrate issue... Trying to render out to Main Concept AAC/AVC (mpeg4 - h264) with a constant bitrate = 5,000,000 bps When I type that bitrate in, it won't stay selected. when I close out and come back, the bitrate (render settings) have changed to 192,000. The drop down menu only lets you select (in that range) 4,000,000 and 10,000,000 -- not 5,000,000 Anybody know why I cannot type in 5,000,000 bps and have it remain and render that bit rate? Thanks --

August 24th, 2010, 11:20 AM	#2
Arkady Bolotin Regular Crew Join Date: Sep 2008 Location: Beersheba, Israel Posts: 111	It is so, because the MainConcept AAC/AVC encoder included into the Vegas 9 has only two profiles to choose – Baseline (BP) and Main (MP). At the level 2.1 (which is the specified set of constraints indicating a degree of required decoder performance for a profile), both BP and MP provide only four Mbit/s for video bit rate. What you need is the High profile (HiP) that delivers 5 Mbit/s at the same 2.1 level. Unfortunately, HiP is missing in the Vegas 9 AAC/AVC encoder.

August 25th, 2010, 06:11 AM	#3
James Binder Major Player Join Date: Jan 2005 Location: NY, NYC Posts: 367	Thanks Arkady -- So to get this straight -- there is no way to output a 5mbps AAC/AVC h264 file? I'm almost certian that in Vegas 8 I could choose that option. This seems strange to me in that this is a pretty basic setting for encoding files to be uploaded to Vimeo and the likes... Can anyone else confirm that this WAS an option in Vegas 8?

August 25th, 2010, 07:07 AM	#4
Arkady Bolotin Regular Crew Join Date: Sep 2008 Location: Beersheba, Israel Posts: 111	Actually, there is. Instead of the constant bit rate = 5 Mbit/s, pick the variable bit rate: type the number 5,000,000 in the Maximum (bps) and Average (bps) fields. Not only will this option hold easy high- and low-motion changes in your video, but it will also be able to produce higher picture quality than the constant bit rate option.

October 4th, 2010, 07:02 AM	#5
James Binder Major Player Join Date: Jan 2005 Location: NY, NYC Posts: 367	Thanks again Arkady. Thought I'd bring this one back. I've been trying this with my exports (headed to Vimeo in specific) and all seems well so far. I am curious to know if this method (by the numbers, under the hood) is providing as good as or superior results compared with the same bit rate CBR? If so (and for the tech inclined here) -- why? By selecting the same min and max number, is one in fact creating CBR -- without any bitrate fluctuation? I know I was able to select 5 mbits CBR in Vegas 8. Why not in ver 9? Thanks --

October 4th, 2010, 04:42 PM	#6
Arkady Bolotin Regular Crew Join Date: Sep 2008 Location: Beersheba, Israel Posts: 111	Hi James: The main advantage of VBR encoding is that it produces a better quality-to-space ratio compared to a CBR encoded file of the same data. The bits available are used more flexibly in order to encode video, with fewer bits used in less demanding passages and more bits used in difficult-to-encode passages. Suppose we have chosen the rate (at which a codec's output data should be consumed) to be constant and equal to 5 Mbit/s. Then it might happen that we had not allocated enough data for a complex scene in our video and as a result we would get an increased blockiness in this scene, because the frames would no longer being fully detailed in their rendering. Sure, that problem could be easily solved by choosing a high bitrate (say 25 Mbit/s). However, such a solution would inevitably enlarge the size of the resultant video file and – what’s more important – could introduce stutter when streaming the file.