Black frame(s) when video loops the first time

[Freddy Komp]

Hi all,


Has anyone else noticed this behaviour? Is it something codec related? Here is the scenario:

I am using a lot of looped/loopable H264 .mp4 files (1920 by 1200 @30fps (not 29.xxx), from AE CS 5.5 / Mac, MainConcept H.264 Video, Profile High, Level 5.1, VBR 1 Pass, Target 5 Mbps, Maximum 10Mbps, Multiplexing MP4, Stream Compatibility Standard), and they loop just fine any 2nd - nth time, but between the 1st and 2nd time, there is a consistent black frame (or several ones?) that flash up. I have tried with loading the video specifically, without, but no difference. It also does not seem to make a difference how long the clip is (between 10 secs and 2 mins), whether it is faded in, whether other items are playing...

It happens on faster and slower machines (running 10.8.5), all of which have SSDs.

It is pretty annoying, since I have just grown to appreciate H264 as a codec that is a good alternative to the large (but in the past rocksolid) PhotoJPEG, specifically to have more manageable file sizes while using native resolutions of Full HD Projectors.

Thanks for looking at this, as this does not look good - I keep thinking of the subliminal stuff from Fight Club :)!


Cheers,

Freddy

[micpool]

I can't replicate your problem, I would however make the following observations

You are rendering out of AE using a rather specialist preset for h264 i.e h264 BluRay. Why not try vanilla h264 as a .mov

Conventional wisdom says: use AE for rendering (to a lossless or HQ codec) and use encoder software to encode your playback material

This means that you have a high quality master of all the work you have done in AE that may have been quite time-consuming to render. You can then quickly experiment with playback codecs by batch encoding these masters to various formats.

5000 kb/s seems a very low target rate for a 1920 x1200 30fps video. Bluray for 1080p would have a target rate of 4-8 times this. 

If you use ProRes LT as your mastering codec, that would give you a good basis for low bit rate encoding, but would also give you a master that Qlab would quite happily play off an SSD or fast HD without any further encoding.

Mic

[Drew Schmidt]

Try using ProRes 422 LT
That fixed the problem for me.
Its a problem of performance.

[Freddy Komp]

Thanks Mic and Drew,

Thanks for the suggestions, I will certainly look into ProResLT again for the future, but the project I am currently working on is across the ocean, which means that the 10fold increase of the data to be transferred ain't exactly fun for either side; Qualtiy aside, What I am having a hard time understanding is the fact that it seems to have no trouble whatsoever the 2nd-nth times of the loop, but canconsistently not get it the first time, no matter the grunt of the machine, no matter the length of the clip... It actually seems to be getting transparent, not black - it something is below, it comes through instead of black.

I was able to solve it now with a quicktime based H264 (although my initial codec was not based on a blueray preset), and with a spatial quality of 10/100, it still seems to look good, with 13MB for 12 seconds busy motion graphics, so that will have to do for now. Still interested though in a comment from figure53 in response to my logic above.

Cheers,

Freddy


Thanks,

Freddy

[micpool]

Regardless of what the preset was called, you were creating a multiplexed stream using a proprietary version of the h264 codec (Main Concept 5.1) in an mp4 wrapper which would not be a usual choice for Qlab playback.

I have found all sorts of anomalies with this type of codec rendering from AE, including  format mismatch flags  renders limited to  to 720x480,  Weird  black frames at the end of files which only show upon QT player  if you slide the transport bar to the end of the video when it's not playing and files that won't play at all.

I would stick to the standard formats and render to QuicktTime.mov format.

To reinforce my point about not rendering from AE to h264  directly, it is interesting to note that in versions after AECS6 i.e CC versions, h264 rendering from the application is deprecated and removed from the normal output options for reasons explained in this forum thread.

https://forums.adobe.com/message/5458515#5458515

[Freddy Komp]

Hey Mic,

I finally came back to this all (same gig like last year, with lots of data across the pond), and after re-reading your post came up with an idea that fixed it (i.e. letting me use incredibly low data rates in H264 with MainConcept and still retain seamless loopability without black frames in it).

While of course this is neither an ideal codec nor practice, I thought it would be worth sharing if anyone else ever finds themselves in a pickle where there have to deal with material that should loop seamlessly but does not:

I used the FFmpeg based iFFmpeg to basically just re-wrap (stream copy) into a mov container. done. retains the same size, loops seamlessly where the .mp4 does not. Thanks Mic again for the inspiration by mentioning the mp4 container as a potential source of issues in your post :).


Cheers,

Freddy