HapQ chunkin'

I don’t suppose there’s a way to ‘chunk’ a HapQ file that isn’t?

My understanding is that the chunking is just an application of snappy to sub-chunks of the frame, instead of the whole frame, to help with multi-threaded decoding (someone should CUDA that shit), so the actual video data shouldn’t need to be touched?

So in theory, a file could be decoded as far as the DXT-5 planes, then re-snappied and put back in a movie?

Hmm. If TouchDesigner can’t do it, I guess it may be possible with a trivial ffmpeg app? Malcolm - any advice on that? I’ve rolled my own HapQ handling code using ffmpeg and lib snappy, so it feels like it would be inside my capabilities (although I rarely make movies with ffmpeg APIs).

Thanks,

Bruce

Hey Bruce,

We do something very similar here in house at Obscura. We use an internal file format called FireFrames which behave like HAP with the advantage of being frame sequences, and allowing for block reading - meaning that only a section of the frame is actively decoded. This is pretty useful for large plates, though there are some frustrating trade-offs.

I’d say that it’s worth chasing if you’re dealing with HUGE resolutions that can’t be cut-up in a typical approach, but in many other situations it’s sometimes more frustrating that advantageous. PM me if that’s too vague, of if you want to chat more

See this old thread how to chunk a HAPQ file in libav and/or ffmpeg.

TLDR; Just add “-chunks 16” to the commandline to encode it into 16 chunks.

I thought TD Movie Out TOP chunks HAPQ movies by default to 12 chunks BTW.

Cool. But I’m actually hoping to chunk something already in HapQ without deciding and re-encoding, which I’d expect to be lossy.

Guess ffmpeg supports the right stuff now, but by default it would do the whole deal. Some ffmpeg Kung fu is my fallback if HapQ won’t do it.

Bruce

I’m not aware of a tool that does this yet. Wouldn’t be too hard if you already have code that does Hap processing.

Hmm, maybe this is moot - looks like chunking got placed into the current release of Hap and maybe even in current QT codec version?

So I’d only ever need to do this to legacy files that I only have in HapQ.

How could I tell if a file has chunked frames?

Bruce