[mythtv-users] Combined FE/BE using USB for all I/O?

[Jean-Yves Avenard]

On 17 August 2014 21:43, Eric Sharkey <eric at lisaneric.org> wrote:

> You know I never said anything like that.  MythTV is a tremendously
> successful accomplishment, but that doesn't mean it's perfect in every
> way and that there aren't parts which can't be made better.  If you
> talk to any developer, I'm sure you'll find dissatisfaction with this,
> that, or the other thing, and some regrets about decisions made long
> ago.  That's the nature of software development and is why there's
> always a new version being worked on.

Really, dissatisfaction? first time I hear about it.

To be honest, we've only been waiting for years to come and fix all
those poorly thought of algorithm.
After all, myth has never been able to record anything for anyone for
over a decade.


> The critical difference is that there's no synchronization to block
> the writing thread from getting arbitrarily far ahead of the syncing
> thread.  There's no fixed size, compile time, same on every system
> limit on the amount of memory used.  With this kind of design, one
> thread reads from the recording device as fast as possible, and
> another thread syncs to disk as fast as possible.  The OS is free to
> schedule the actual disk I/O in ways that it sees fit, even if that
> means delaying writes for a particular block by multiple seconds
> (which would have caused a fixed size buffer to fill).  In other
> words, the buffer size scales dynamically with need, never larger nor
> smaller than necessary.
>

Before talking about what a system does, it may be worth actually
knowing what it does. You can either look at the source code
(libs/libmythbase/threadedfilewriter.cpp

You will quickly realise your assumptions about what mythtv does are
wrong, making most of your comparisons totally irrelevant.