Changing render file size

airport wrote on 2/20/2012, 11:48 AM

I have a ts file of 12.5 gigs which I edited by removing about 15 minutes from. I then rendered to blu-ray with average bit rate settings and got a file of 24.5 gigs in m2v plus the mpa file. I rendered again with a lower setting on the slider and reduced the project setting from best to good. The rendered file was exactly the same size. What do I set to create a smaller final file size?

VB1

Comments

TheHappyFriar wrote on 2/20/2012, 12:42 PM

Your bitrate needs to be lower. bitrate is proportional to file size.

Chienworks wrote on 2/20/2012, 2:20 PM

Also i'll point out that the quality slider doesn't affect the size of the output much, but merely specifies how much effort the encoder puts into "getting it right" when compressing. Higher quality encodes will take longer and will look somewhat better, but they won't be bigger than low quality encodes.

johnmeyer wrote on 2/20/2012, 2:27 PM

Just to reinforce and build on what HappyFriar said: not only is file size proportional to bitrate (i.e., double the bitrate and you double the file size), but it is the only thing that determines file size.

The quality sliders change how long the encoder takes to create the video, because at higher quality, the encoder looks at more frames to determine inter-frame encoding values. However, in the end, the number of bits per second is what accumulates to create the final file size.

[edit]I see Kelly said the same thing while I was writing ...

Former user wrote on 2/20/2012, 2:29 PM

and just to expand on JohnMeyer, LENGTH of program and BITRATE determine file size. ;)

Dave T2

johnmeyer wrote on 2/20/2012, 2:32 PM

and just to expand on JohnMeyer, LENGTH of program and BITRATE determine file size. ;)Yup!

airport wrote on 2/20/2012, 7:04 PM

Thanks to all. It worked. Is there any way to guess what the final file size might be and how to decide how much to reduce the bit rate? Also, why is the output twice the size of the ts input?

VB1

farss wrote on 2/20/2012, 8:04 PM

"Is there any way to guess what the final file size might be "

Divide megabits per second by eight to get megabytes per second of video.

"why is the output twice the size of the ts input?"

If the source ts file was recorded at 8Mbps and the output was encoded at 24Mbps then assuming both were the same duration the output file would be three times the size of the input file.

Bob.

Chienworks wrote on 2/20/2012, 8:11 PM

Or ... more succinctly ... it's all dependent on the bitrate.

And yes, bitrate applies to the source file exactly as it applies to the output file.