Quality Setting vs Bitrate Setting?

[krwzmann]

Hi all. Can someone share some info on the difference in the end product when comparing the settings of the 'Quality' (1-100) setting vs 'bit rate setting (5000-9000kbps).

I usually render with 100 quality and depending on the length of my clips i'll use either use constant bit rate 6000kbps or for shorter clips 8000kbps. I'll go with 6000 for longer clips so that I can fit all the chapters I need onto just one disc. With the shorter clips, i'll go for more quality and stick with a higher bit rate. I do notice the video quality difference between 6000kbps and 8000kbps. I also do notice that there is a big difference in space used to render.

My question is, would I have better quality/space saving results if I set the quality to 90 instead of 100 and then going with a higher bit rate (7000 instead of 6000)?

Quality 90 / Constant Bit Rate 7000kbps
vs
Quality 100 / Constant Bit Rate 6000kbps

Who wins the quality + space usage battle?

Thanks!

[DVDDoug]

I don't know what the "quality" setting means, but I’m always willing to guess!

I can think of 3 things that affect quality:
- Bitrate.
- Resolution (the number of pixels per frame).
- The encoding algorithm.

With variable bitrate, it could be a variation in how low the bitrate goes, and / or what percentage of the time the bitrate is high or low.

Or, to the extent that “quality” is independent from bitrate, It might be a rendering-time trade-off. A really good 2-pass algorithm will take more time than a quick and dirty algorithm.

[Devil]

Quality 90 / Constant Bit Rate 7000kbps
vs
Quality 100 / Constant Bit Rate 6000kbps

Who wins the quality + space usage battle?

There's one way to find out: try it under your individual conditions of use!!!

[krwzmann]

I just thought maybe someone would know straight up the difference. I just wonderied that since there is a Bit Rate Setting, and the Bit Rate affects the quality of the video, why is there even a seperate Quality setting.

Oh wellpz, i'll just stick to what works until I can find time to experiment.

[GeorgeW]

Quality 90 / Constant Bit Rate 7000kbps
vs
Quality 100 / Constant Bit Rate 6000kbps

Who wins the quality + space usage battle?

With CBR and assuming all other things are equal, the space battle is easy -- the lower bitrate will need less space.

Quality is a different story. In general, the higher bitrate will allow the encoder to use more bits to represent your video. However, the quality slider is the key difference (in your question). The higher the quality slider, the more time the encoder will take to come up with the best way to encode your video. If I were to guess, in your example the 7000kbps encode at 90 will look better than the other. But, a 7000kbps at a quality setting of say 30 might actually be worse than a 6000kbps at Q100.

Regards,
George

[sjj1805]

OK we are looking at Media Studio here but....

Page 179 of Video Studio Manual

Speed/Quality: Drag the slider to control the compression of a file. Dragging the slider to the right produces a higher quality video but at the expense of fluid motion of the video. Dragging the slider to the left produces a fluid motion video but at the expense of quality of the video.

Page 180
Quality: Drag the slider to control the compression of a file

Steve J