[FFmpeg-user] Simultaneous two-pass?

[Jesse Gordon]

On 09/27/2012 04:50 AM, Carl Eugen Hoyos wrote:
> Jesse Gordon <tojesseg <at> gmail.com> writes:
>
>>>> But that's OK because whenever a user uploads a video, it
>>>> has to be converted into half a dozen different sizes and
>>>> rates to accomodate viewers with different internet speeds,
>>>> so I can just launch several instances in parallel.
>>> I suspect this should be (significantly?) faster if done
>>> in one FFmpeg instance.
>>>
>> Well, I'm encoding to flv which does not support any threading, and I
>> have 8 cores.
>> So I can clearly get more work done faster by running several ffmpeg
>> instances at the same time.
> What I meant is that you can the save 6% that decoding costs for
> every of your instances by encoding to all needed resolutions
> at the same time.

Carl,

Than you very much for the reply. It looks like the decoding part is 
using 60% of one CPU - so it would be good if there was a way I could 
decode only once and then re-encode to all the needed resolutions from that.

But how would I do that? Decode first to a raw format on a ramdrive, 
then re-encode from there? Or can one instance of ffmpeg write multiple 
streams encoded at different rates?

>
> (It will of course not be significantly faster if your input
> file is so "cheap" to decode but there may be other source files.)
>
> Please leave an empty line between your quotes and your replies
> (and between the "old" quotes), that makes reading your mails
> much easier.

Thank you for the empty-line tip - it does help a lot!

Thanks very much,

~Jesse Gordon

>
> Carl Eugen
>
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