Problems Encoding 95 minute Movie for Blu-ray in h264, sample pics inside

[Zak Forsman]

I'm trying to create a Blu-ray master for festival screenings. My first attempt was in Adobe Media Encoder CS5.5 and this resulted in dark and light blocks that flicker and flutter throughout the movie. The movie plays fine but every ten seconds or so, a portion of the frame will exhibit a rectangular block that flashes a touch brighter or darker for the duration of a single frame. It's subtle but there giving the feeling of an unstable image. Here are some sample at 1080p.

NORMAL FRAME
FRAME WITH A LIGHT BLOCK
FRAME WITH A DARK BLOCK

My encoding settings are as follows:

video codec: main concept h.264 for blu-ray
target bitrate: 30
max bitrate: 35
profile: high 4.1
encoding VBR, 2 Pass

and I've tried all variations of checking and unchecking "Max Render Quality" and "Max Depth" with no changes. I've switched from High profile to Main with no change. I've attempted the same thing in Apple Compressor, same image problem. I have looked very closely at the ProRes master for the slightest fluctuations and see absolutely nothing.

So far, I have only found two ways to fix this...

First, by setting the Key Frame to a value of 1 (which i believe negates the efficiency of the h264 codec) the flashes and flickers and flutters more or less go away. Not 100% perfect but they're essentially gone.

The second solution is to encode with MPEG2, an older codec that doesn't seem to hold up as well on fast motion, but is delivering a better overall image. It's rock solid stable but a little weak on fast motion.

MPEG2 ENCODED FRAME

My settings for this in Apple Compressor are as follows...

video codec: mpeg2 for blu-ray
target bitrate: 30
max bitrate: 38
motion estimation: best
encoding VBR, 2 Pass

I'm perfectly happy to go with MPEG2 despite its flaws, but wanted to see if anyone out there had a similar experience attempting to encode their feature in h264 for Blu-ray. I assume the heavy film grain is the culprit. Also wanted to know if anyone has experienced issues playing at high bitrates like this. Having the player choke on it in the middle of a screening would be one of the worst things to happen in the middle of a screening. I'll test it here of course, but you never know what the festival will be using to playback from. Unfortunately, dropping the target bitrate makes for a noticeable drop in image quality.

 

[arco1]

My thinking is that "heavy film grain" means that every frame is significantly different from nearby frames. By definition, this will make it dificult for any spacial encoding scheme, especially 'more efficient' ones like H264. Blueray encoders like H264 (and mpeg to some extent) are able to use less storage space because they do not completely store every frame. Rather, they record all of each 'key' frame, then record each successive frames' difference from the key frame. This is also why fast motion causes a problem for these encoding techniques.

You could experiment with the relation between target and max bit rate or with setting the max bit rate higher (not sure that is possible.) Otherwise, you'll need to either reduce the film grain, or use more storage space.


Jim
Colorburst Video

 

[Zak Forsman]

Thanks, I've done some experimentation using x264 and it appears to have solved all my problems. The nice thing about it is you can tune it for "film" and even "grain". the results have been stellar thus far.

 

[Postmaster]

How do you fine tune it for film/grain?