Just thought I’d post a few observations/issues that I’ve made when processing my footage using the Sorensen 2 Codec…
Raw footage started as PAL DV.
I imported this into Icarus to stabilise it, as it had a small amount of camera shake on it, and saved the result out as raw JPG frames.
I then re-encoded the frames using the Sorensen 2 codec, with a keyframe every 10 frames. This produced stabilised footage in a MOV file.
Call this ‘mov_in’.
I then used ‘mov_in’ as an animated background plate in C4D, with some CG elements over the top of it, and got C4D to render the results out again using Sorensen 2, this time with a keyframe every 25 frames, quality=high. Call this ‘mov_c4d’.
Results ‘movc4d’ looked ok, EXCEPT that every tenth frame (i.e. corresponding to the keyframes in ‘mov_in’) was noticeably brighter than the other frames. Noticeable colour banding was also present in all frames.
As a comparison, I then tried loading ‘mov_in’ into After Effects 5.0, and rendering the output again as a Sorensen 2 file with keyframes every 25 frames, quality=hig (so basically just transcoding from Sorensen to Sorensen). Call the output ‘mov_ae’.
In ‘mov_ae’, EVERY frame was overbright in the way that every tenth frame in ‘mov_c4d’ was.
I then repeated the C4D and AE tests but using the raw jpg image sequence as input (thankfully C4D supports this!), and the results were both fine.
Although C4D and AE produced different problems, both produced bad output through the Sorensen codec when the source footage was also Sorensen encoded. This suggests that the problem is with the codec rather than either of the apps.
Sorensen 2 seems to have problems when re-encoding footage that was decoded from a Sorensen 2 source.
Since the decoder and the encoder are completely seperate processes, I can only assume that the encoder produces artefacts in the images which the encoder is susceptible to.
Actually, the other possibility is that it is the Quicktime player that is at fault, although most of the work there is being done by the codec again.
In a different project I was tearing my hair out trying to figure out why in two identical compositions rendered from after effects (Soresen again as it happens), one of them seemed not to apply the gamma correct that I’d applied, and the other one did.
I spent ages cursing After Effects for not rendering the same as it was previewing. Then I noticed that although one movie was clearly darker than the other when viewed side by side in two quicktime windows, which one was darker depended upon which order I opened them in. In other words it was a playback problem, not a rendering problem.
One final comment, here’s a tip for reducing file sizes whilst keeping decent quality:
It seems that you can push things a long way by setting keyframes to be very infrequent - at least when there’s not much motion. It remains to be seen what adding camera shake does for the compression - depends how smart they are…
Anyone else have any comments on any of this?
Bye for now!