On Aug 20, 2015, at 1:03 PM, Alice Wonder <alice@xxxxxxxxxxxxxx> wrote:
>
> On 08/20/2015 10:27 AM, ken wrote:
>> On 08/20/2015 10:27 AM, Alice Wonder wrote:
>>> I bought a BluRay for my Thinkpad and my Desktop.
>>>
>>> Very rarely use them, but on occassion I do.
>>>
>>> When I use them, I use them to rip movies via MakeMKV but honestly that
>>> is the only BluRay use they ever get. And mostly the desktop, the laptop
>>> doesn't have the memory to encode hi def in reasonable amount of time.
>>
>> How much memory do you think would be needed to do that?
>
> I don't know, but my desktop has 16 GB and the laptop only has 4 GB (and a slower CPU)
An uncompressed 4:2:0 frame of 2K video takes about 2.5 MiB of RAM. If you represent it as 4:4:4 during recompression instead, it’s 6 MiB. An H.264 encoder might need a dozen or so frames in RAM at a time to do the inter-frame compression, so you’re talking about something like 30-100 MiB of RAM.
Some encoders are inefficient, and grab a gig or so of RAM, but I expect that’s only because they can get away with it these days.
It’s possible to be much more efficient, evidenced by the fact that so many smartphones and digital cameras have H.264 encoders in them. You don’t imagine they have a gig of RAM sitting around just for the H.264 encoder, do you?
The main thing you need for fast video encoding is one of:
a) multiple fast general-purpose CPU cores
b) lots of GPU pipelines, or
c) a dedicated hardware ASIC (or equivalent in die space on a SoC)
It’s all down to processing power, not RAM.
Video encoding is a big reason that the Intel Core i7 made such a big splash about 5 years ago. It’s one of the few desktop applications that can make effective use all those fast cores. GPU encoding has also made great strides recently.
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