INTERACT FORUM
More => Old Versions => Media Center 16 (Development Ended) => Topic started by: MrC on August 29, 2011, 05:34:02 pm
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It appears there is no caching of file tags, which makes using Tag() in an expression column pretty rough going.
Just out of curiosity, I wanted to check my REPLAYGAIN_TRACK_GAIN tags against [Replay Gain], and found that it took several minutes to display the expression column:
Tag(REPLAYGAIN_TRACK_GAIN)
Once populated, clicking a single entry in the column took several more minutes, so it seems MC rescans the physical tags again for ALL 17k+ audio files. And again for any other operation.
Can MC cache these values once looked up, at least while they are in a view?
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It appears there is no caching of file tags, which makes using Tag() in an expression column pretty rough going.
The database is the cache. Using [Replay Gain] will be very fast. Using Tag(...) will go to the physical file.
If you sort, it is careful to only evaluate the expression once per file.
I don't think adding a caching layer to expressions is a great idea, because some expressions change with time with Counter(...), or do other things where a caching layer will cause trouble.
In general, use expressions sparingly. They are an order of magnitude slower than using the database directly.
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I probably wasn't too clear. I'm on-board with the internal DB fields/values vs. the physical tags/values distinction, and how MC uses them.
(But your answer I think hints to me more about how MC is working internally to present pane column data initially and after each selection)
I was interested in exploring a physical file tag for all files, in this particular case, REPLAYGAIN_TRACK_GAIN. Out of curiosity, I was going to compare those tags with [Replay Gain] db values (taking into account the 6db change, of course).
Doing this, I happened to notice that some REPLAYGAIN_TRACK_GAIN file tags had " db" after the decimal, and recall Alex (I think) mentioning this many moons ago. I also recall there was some change a while back in the way MC wrote out various gain tags, so I simply wanted to compare, mostly to see what worked.
So I created a Tag(REPLAYGAIN_TRACK_GAIN) expression column as a test, to grab the values so I could see them all. But selecting anything in the panes column takes too long to be useful. It seems the column expression is re-run to obtain the selected file list. I was thinking the content of panes was cached, and making a selecting just winnowed those results.
But, as you suggest, using the expression in the File list, although painful the first run, is fine afterwards.
I agree, adding a caching layer is not necessary, especially not for my unorthodox uses. :-)
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One thing you can do is create a user library field. Let's call it "MrC".
You can then devise some fancy expression. Pick all your files, and edit the field "MrC" with =[insert fancy expression here]
This will store the result of the expression for each file. It may take a little while, but will only evaluate the expression once for each file.
After that, you can use the field [MrC] for sorting, searching, in views, etc. and it will be fast.
In essence, this creates a caching layer that you can control as the user.
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I've become so accustomed to the speed of your Regex() implementation and using my new fancy views for instantaneous access, that thought hadn't yet found its way into my Neanderthal skull.
A perfectly fine solution, thanks.
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So it appears that Tag(REPLAYGAIN_TRACK_GAIN) will remove the 6db bias from the physical tag.l
Is there a way of returning a raw, unbiased tag value? Eg:
Tag(REPLAYGAIN_TRACK_GAIN, 1)
where 1 says Don't Muck with Me.
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So it appears that Tag(REPLAYGAIN_TRACK_GAIN) will remove the 6db bias from the physical tag.l
Is there a way of returning a raw, unbiased tag value? Eg:
Tag(REPLAYGAIN_TRACK_GAIN, 1)
where 1 says Don't Muck with Me.
Not really. Input plugins always return data in the format the program expects.
This is a matter of degrees, since the "raw unbiased tag value" is really a blob of binary data.
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Got it.
So the Tag dump contents in the Tag Action Window must be already formatted and handed to MC by the input plug in...