OpenCL Snow Leopard / HandBrake

HandBrake for Mac support
Forum rules
An Activity Log is required for support requests. Please read How-to get an activity log? for details on how and why this should be provided.
Post Reply
ACiB708
Posts: 5
Joined: Tue Jun 02, 2009 9:00 am

OpenCL Snow Leopard / HandBrake

Post by ACiB708 »

Hey all, just wondering, and I know it's still a bit early to ask (I did not find any info regarding this topic, well just one post but it did not actually answer the question)... Will HandBrake support OpenCL in Snow Leopard? Supposedly it significantly increases h264 encoding... Just wondering...
User avatar
s55
HandBrake Team
Posts: 10350
Joined: Sun Dec 24, 2006 1:05 pm

Re: OpenCL Snow Leopard / HandBrake

Post by s55 »

Not right away. If the underlying libraries take advantage of it, then HB will, but it's not something that will happen overnight. It'll probably be a long wait.
hunterk
Bright Spark User
Posts: 179
Joined: Tue Jun 03, 2008 2:27 pm

Re: OpenCL Snow Leopard / HandBrake

Post by hunterk »

Just to add a little bit of information regarding x264 on a gpgpu platform (such as OpenCL) for anyone who's interested: Dark Shikari, one of the lead developers for the x264 library, has been working on this for a while, initially with the goal of porting x264 to Nvidia's CUDA platform. However, he soon found that the parallelization in x264 just doesn't scale up enough to make it worthwhile (x264 scales almost linearly to approx 16 cores, but gpgpu applications don't really shine until parallelization reaches something like 128+ threads, IIRC). There is still some effort to offload motion estimation to the GPU, but it hasn't panned out yet. AFAIK, that's the only calculation that stands to benefit significantly from the offloading.

Other companies that have claimed drastic speedups to h.264 encoding are not really telling the whole story. Generally, they are either accelerating mainline h.264, i.e. with no optimization and therefore horrible quality, or they are comparing it to the H.264 Reference Encoder, which is woefully slow compared with x264 anyway.

(much of this is covered in Avidemux's H.264/AVC Options Explained document)

I have personally never seen any true apples-to-apples comparisons of x264 vs an accelerated solution, with high quality held as a prerequisite. In my brief experience with Badaboom, a CUDA-enabled encoder, the options are so obfuscated, there's no way to know which optimizations--if any--are being used to make a real comparison.
ACiB708
Posts: 5
Joined: Tue Jun 02, 2009 9:00 am

Re: OpenCL Snow Leopard / HandBrake

Post by ACiB708 »

Well, thanks a lot for the help... It´d be great to see it implemented on an already great piece of software.
davidahn
Posts: 7
Joined: Tue May 22, 2007 5:25 pm

Re: OpenCL Snow Leopard / HandBrake

Post by davidahn »

Not to state the obvious, but I hope it maximizes the CPUs as well as the GPUs, especially for those with multi-core Mac Pros, or at least to have that option (CPUs only, GPUs only, both).

I for one would LOVE to see this happen! Great job, guys. I've been looking forward to HD video support for a LONG time. I tried other products, but found them to be somewhat flaky.

David
Post Reply