[mythtv] RE:Re: [PATCH] Increase block size

Mark Frey markfrey at fastmail.fm
Tue Dec 23 18:43:44 EST 2003


Bruce Markey wrote:
>But just to make sure we're on the same page =). First, the
>pre-requesting of data has been there for many months and the
>limitations of the QSocketDevice just showed up a couple weeks
>ago. This was a much slicker idea before there was a 130k limit.

Now you see, I just started using MythTV a couple of weeks ago, so I missed
the glory days of pre-requesting :-D
But much of the previous code certainly makes sense to me now.

>Say the bitrate a user sets for live TV equates to about 1MB/sec.
>which would be about 3.6GB/hour. For the read to return 256000
>it needs 256000 bytes of data. This data won't exist until it's
>recorded about 0.25sec or about 8 frames.
>
>Now lets say she sets her bitrate for 0.9GB/hour or 1/4MB/sec.
>Now the encoder needs to run for a full second in order to have
>256000 that it can return. If the block size was 64000 it would
>again take 0.25sec. Therefore the different in blocksize adds
>0.75sec to every channel change.

Yah, I completely missed this effect. I was only considering the actual
transfer rate/time regarding channel changes. Hey, that's what you and
Avalanche are for right? Thanks to both of you for the input and changes,
etc.

-Mark



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