Tests at the low end of the bandwidth revealed that AVC (x.264) does not offer significant advantage over ASP(XVID, DX50). It did looked better overall, but not good enough to justify 50% increase in speed required to both encode and decode. Once again the test were at the low end of the bandwidth where all codecs showed some but yet noticable artifacts. This low end of the bandwidth is as follows
| Size |
Bandwidth |
QT7 on 848Mhz CPU |
| 384x288 |
300 kbps |
80-85% |
| 480x352 |
500 kbps |
90% |
| 640x480(480p) |
800 kbps |
100+% |
Encoding bellow those rates yeilded significant artifacts. Interestingly enough, 480x352 at 500kbps is right at the edge of “having not enought bandwidth” (test to see if 600kbps is really needed for 480x352) and in this case DX50 gave better results then X.264 due to that artifacts were more noticable with X.264 then DX50 (Both have more artifacts then 384x288 @300kpbs).
As for 480p or 640x480, with noisy sources that I've got it looks like 800 kbps will not be enough. How much would it take? 900kbps? 1000kbps? Streaming 480p is out of the question, or isn't it?
Note that on 848 MHz CPU H.264 as well as DX50 decoding is not real-time (100% CPU).
Overall quality wise, codecs ranked as follows
- x.264
- DX50 2 pass
- XVID 2 pass
- XVID single pass