View Full Version : optimal bitrate

05-13-2008, 06:24
Hi all,

I want to know what the optimal video bitrate is such that using anything higher would merely be wasting storage capacity. I will only be using the videos to view on the D2's display.

At the moment I'm encoding my video files at 720 Kbps, but I think this may be excessive. Any ideas on what is a good bitrate to use?

05-13-2008, 06:58
I've been happy with bitrates about half that. But that's me.

I'd suggest you make some movies at different bitrates and see if you notice any difference.

05-13-2008, 07:01
I was hoping someone would give me a definite answer to save me time experimenting with different bitrates :-)

05-13-2008, 08:11
if you don't want to wait for the conversion to go through the whole video, select source options and define a range for conversionen (few minutes).
Its perfect for testing!

05-13-2008, 09:38
I was hoping someone would give me a definite answer to save me time experimenting with different bitrates :-)

I did give you a definite answer: I said I used bitrates about half of yours. But a lower bitrate means a less-well-defined picture, and you have to decide for yourself if the tradeoff is worth it.

And that means a little experimenting on your part... sorry.

05-16-2008, 13:52
Another thing to consider is the source of what you are converting. Animation vs Live Action could require a different bitrate to look acceptable. Movies with a lot of dark scenes typically use fewer bits. Also, widescreen video requires less bitrate than full screen as you are filling less of the screen. The tool used, filters, output type (avi, wmv) all factors into the bitrate needed for an acceptable quality.

I agree with Bob, you should do some short test encodes with various movie types to determine what looks best to you. And you really need to view the movies on the D2 to judge quality. There is a noticeable difference between viewing movies on a CRT, LCD and the D2, with the LCD and D2 being fairly similar.

Here a few samples of the bitrates of some movies I've encoded recently. I encode using AutoMkv with Constant Quality instead of a Target Rate, but at least you'll have some ideas of the rates that appear good to me. I tried some test encodes with a lower quantizer value, it gave me a much larger bitrate without a noticeable improvement in quality. I have recently been able to get my file sizes down by using some filters in AutoMkv (FluxSmoothST, FFT3DFilter, RemoveGrain). The drawback is that the conversion time grew quite a bit. Note that I had to create a custom
profile and tweak the settings of AutoMkv to get videos to play properly on the D2.

Xmen - 320x144 - 258Kbps
Xmen2 - 320x144 - 272Kbps
Shrek - 320x176 - 295Kbps
Phantom Menace - 320x144 - 384Kbps
Friends Episodes - 320x240 - 350Kbps - 600Kbps, mostly above 500Kbps though.

05-16-2008, 16:01
The funny thing is, that when i choose "best quality" (on jet thing video converter) the new video for d2 is even bigger than the original :D

06-05-2008, 06:26
thats quite logical...

first of all you can decode a low quality movie in a higher resolution which makes it bigger without any quality improvement.
Secondly the D2 does not have much cpu power (comperd to a normal pc), so the videos can not be compressed very good, i.e. no B-Frames are supported.