On Aug 30, 2012, at 8:08 AM, Camera Man wrote:

> On 08/29/2012 11:53 AM, Mark Kenna wrote:
>> Can someone tell me how a conversion for live streaming is possible? Also, I 
>> would be doing the file conversion dynamically in memory which means that I 
>> cannot just encode a file, re-position the MOOV atom and then stream.
> 
> If you can estimate the needed size of the moov atom, you can reserve space 
> with the -moov_size option (added in the last year, I think); this would 
> remove the need for qt-faststart and friends, and you could do everything in 
> one pass. (There will be wasted space for sure, but if your estimate is 
> reasonable it will not be too bad)

I missed that. Is there a programmatic option to reserve space for a moov atom 
too?

I think I need to know the number of frames/packets to know the atom size, but 
don't need to know the size of data in each packet, right? So a re-compression 
to a different codec could be accomplished this way?

Bruce


> 
> Do note, however, that ffmpeg will only write that MOOV atom after all the 
> data is in the file, so it will not let you start streaming any earlier than 
> you could with qt-faststart or mp4box.
> 
> If you want immediate live streaming, perhaps HTTPLiveStreaming (HLS) will be 
> better for you. If you want MP4 output, you'll have to finish making the file 
> before starting to play it, regardless of whether it plays immediately when 
> it starts streaming.
> 
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