[mythtv-users] Question about recording profiles - bit rate vs max bit rate

Brian L. Walter blwalter at gmail.com
Fri May 11 10:47:41 UTC 2007


Michael T. Dean wrote:
> On 05/10/2007 08:23 PM, Brian L. Walter wrote:
>   
>> Pardon the ignorance but I'm wondering what is the difference between 
>> the bitrate you set for a transcoder,
>>     
>
> average bitrate
>
>   
>>  and the max bitrate...
>>     
>
> hard upper boundary
>
>   
>> and how do 
>> the two interact?
>>     
>
> generally by a bit of black magic it seems.  But, the encoders do a 
> pretty good job of keeping the average bitrate relatively close to the 
> value specified for reasonably-long videos (i.e. > 10 minutes or so).  
> The max bitrate needs to be around 4/3 the average to allow headroom for 
> fast-moving scenes and scene changes.  There's a point at which 
> increasing the max bitrate will have no positive effects (and some may 
> argue can create issues for the encoder), so more isn't necessarily better.
>
> You can do tons of research to find "the right values" to use or just 
> adjust them until it looks good to you.  After all, in the end, that's 
> really what matters...  Note, also, that bitrate--and only 
> bitrate--determines file size, so you're aiming for a good balance of 
> quality and file size.
>
> Mike
>   
Thanks!


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