640x480 500 kbps at 20 fps

Looks like for home videos h.264 640x480 500 kbps at 20 fps is the best compromise between size and quality.

Going to full frame rates would require 25%-50% more bandwidth that is full framerates need 650 kbps for PAL (25 fps) and 750 kbps for NTSC (29.97 fps). You really cannot go lower then 20 fps because motion becomes jerky. Going to smaller picture size 480x352 doesn't buy that much - 400 kbps vs 500 kbps. Well, sometimes it could be pushed to 300 kbps, but it is a smaller picture after all and besides when outputing to TV it result in "scaling artifacts".

Sometimes thought 500 kbps is not enough to encode at 640x480, like with Dance video, but 400 kbps at 480x352 could be enough (not enough with Dance video, or is it???). And sometimes 500 kbps is not enough even for 480x352 (PomPom). At this time I don't know how to handle that, but both videos have "a lot of black" and "a lot of motion" in common.

So for now the game plan is

1. Encode 640x480 at 500 kbps
2. Encode 480x352 at 300 kbps
3. If could be pushed bellow, do the push.

The following table list 480x352 clips that I uploaded so far

clip	kbps	PSNR
Udarenia	250	34.95 (60.84SSIM)
Gazon	300	38.674/38.290	8.68/5.92fps
Bike	400	35.73 (60.05SSIM)	lower there were artifacts
Bike	350	37.104/36.890	8.07/5.64fps
Dance	400	40.63 (76.70SSIM)	cannot be pushed lower
Podcast	300	36.465/36.372	8.09/5.74fps
Svekla	300	37.516/37.410	11.30/7.03fps

As could be seen out of 6 clips only 2 needed 400kbps and average encode speed for 2 pass x264 encoding was 1/8+1/5.7=1/3 ~ 3.32 FPS. With exception of "Udarenia" clip (which is old unreliable number) PSNR was higher then 35.

The following table shows the metrics for 640x480 @ 500 kbps

clip	kbps	PSNR
Udarenia	500	35.61 (60.84SSIM)
Gazon	500	38.52 (47.52 SSIM)	8.06/4.31fps
Bike	500	37.09 (54.25 SSIM)
Dance	500	38.17 (65.76 SSIM)	7.26/4.23fps
Podcast	500	38.006/37.135	4.97/3.45fps
Svekla	500	38.250/38.147	10.36/5.26fps

As could be seen, when PSNR goes close to 38 at 640x480@500kbps, the clip could be sqeezed to 300kbps at 480x352, with PSNR bellow 33-35 at 640x480@500kbps, the clips could not be sqeezed into 400kbps at 480x352.