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Author Topic: Read from memory  (Read 3509 times)

Blue Boy

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Read from memory
« on: August 16, 2010, 03:51:27 pm »

Hello everybody,

I'm still learning everything about MC and wonder what is the use of read from memory vs read from (I quess) HDD? Is there any difference soundwise? In what situation is the memory option
useful?

I think that I dicovered that my system is more stable when reading from memory is used, but I'm not shure, an answer would be very welcome.

Conny T
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Vincent Kars

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Re: Read from memory
« Reply #1 on: August 16, 2010, 05:29:33 pm »

For optimum sound quality you must feed the right bits (any manipulation will alter the sound) at the right time. Any variation in timing will have a negative impact on sound quality (jitter).
There are many claims that electrical activity going on inside a computer can disturb the clock of the DAC (or the SPDIF out).
As a consequence, minimizing electrical activity will have a positive impact on sound quality by reducing sample rate jitter.
An option is to read the entire song in memory first before playback starts.
This will eliminate the head movements of the disk during playback.
The purist will of course require a HD spin-down too….

Is this the usual audiophile nonsense?
Most of these claims are not backed by any measurement or ABX testing making it impossible to verify them.
Recently I found an interesting piece of information


Obvious there is a difference in jitter between the player in stopped mode and when playing. A spinning optical drive has its impact.
If we look at the values even when spinning, they are very low. So low I doubt this is an audible difference.
But it demonstrates the principle.

How do we translate this to  the impact of head movements of a HD?
I can’t tell you.

My advice in situations like this is:
-   take some very good recordings
-   play them with/without memory playback
-   if you don’t hear a difference then don’t bother.

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Blue Boy

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Re: Read from memory
« Reply #2 on: August 16, 2010, 06:57:13 pm »

Thanks for your answer, I will try to play in both mode to find out if there is a difference (I doubt I can hear any difference) But it seems to me that MC is more stable when reading from memory, can you confirm that or is this noncense of my behalf?
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Matt

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Re: Read from memory
« Reply #3 on: August 16, 2010, 07:13:38 pm »

But it seems to me that MC is more stable when reading from memory, can you confirm that or is this noncense of my behalf?

Media Center should be perfectly stable regardless.  If you've having stability problems, please start a new thread with details and we'll try to get to the bottom of it.

Thanks.
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Matt Ashland, JRiver Media Center

Frobozz

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Re: Read from memory
« Reply #4 on: August 17, 2010, 01:13:57 am »

Is this the usual audiophile nonsense?

I think so.  But the feature is also harmless.  It does no harm to enable the feature.  No harm, no foul.  The biggest benefit is that Matt had fun writing the code to do it.  So in the end it's a good feature.

The concerns I would have would be about what happens if you load a very large file.  Could loading that large file force the OS to page out memory to the page file to make room, thus creating the type of disk activity that you're trying to avoid?  Could loading up RAM with a large file cause the disk cache to flush and also cause the disk cache to reduce the size of its read-ahead cache, thus create more disk activity?  There's lots of potential side-effects from loading a very large file into RAM all at once.  Modern operating systems are incredibly complex.  So many interactions.  They're always busy doing something even when idle.  Just handling all of the system interrupts and dealing with the often sloppy driver code that needs to constantly run is complex enough.  Optimizing a system like that for audiophile tweaker needs is almost futile.

It is something to worry about only after the rest of the computer playback is all optimized.  After the computer is already doing playback 100% reliably glitch-free at low latency.  After the OS has been tweaked to disable unnecessary services and otherwise optimized for audio.  And on a computer that is dedicated to only audio playback.  A computer that sits on the component shelf of the stereo system and does nothing other than play audio.  And for the uber-geek who has access to the necessary tools and licensing, running a customized build of Windows 7 Embedded that has been optimized for audiophile playback.

And in a system where you have no faith in your DAC to properly handle low levels of jitter.  If the DAC is properly handling the inevitable jitter in the signal it gets then what difference does it make if there is very very slightly more jitter for it to deal with?  It all gets cleaned up the same.  But that's engineer thinking and not audiophile thinking.

In the end the feature does no harm so I have no issue with the feature being added.  I'm just not in agreement with its potential benefits.
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Vincent Kars

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Re: Read from memory
« Reply #5 on: August 17, 2010, 03:42:35 am »

Quote
Could loading that large file force the OS to page out memory to the page file to make room

I tested this feature with 14.0.155
The amount of memory MC allocates is limited to 256 Mb.
Indeed Win will use the pagefile if needed.
The answer is to disable the pagefile.
On a dedicated audio PC with sufficient memory you can do so without a problem.
At least mine is running this way.

From a audiophile point of view:
- amount of allocated memory is to low. Should at least be able to contain an entire CD (for those who rip a CD to single file with cue-sheet). Not to mention those who upsample redbook audio off line to e.g. 24/176.
Preferably this should be user configurable. If you run Win64 you can use memory > 4 Gb.
- decoding should be done when loading the track. This will minimize CPU during playback.
Differences in sound quality between WAV and FLAC are often explained by the difference in CPU needed. This feature will effectively eliminate this, great argument if you want to position MC as the audiophile playback platform of choice.
- Start of the playback should be user configurable (wait until song fully loaded or start right away).

In other words, if you go the audiophile way, go all the way.

A nice test: MC starts playback immediately. At a certain moment the song is fully loaded and I/O stops. This is the moment you should hear a change in sound quality. Good luck!

Btw: you can easily check what this feature is doing. Start the Resource Monitor and watch Memory and Disk.
Some screenshots: http://www.thewelltemperedcomputer.com/SW/Players/MC14/MC14_Memory.htm

Blue Boy: I haven's noticed any difference in stability related to this feature
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Frobozz

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Re: Read from memory
« Reply #6 on: August 18, 2010, 01:10:02 am »


In other words, if you go the audiophile way, go all the way.


Yes.  The play from memory feature does beg for more tweaking options.  It's a feature for people who want to get under the hood and mess around in an attempt to find better sound.  Options like being able to set the size of the buffer/cache, choose to have the file decoded to WAV in RAM before the song starts playing, and the other things you mentioned.  It would also be beneficial to be able to have two or more songs (or the entire CD) buffer to RAM so you'll be able to do proper gapless playback with all of those RAM buffering options.  Gapless is important for classical music and of course the Pink Floyd.  Don't want to sacrifice gapless playback just to be able to do the full monty RAM playback stuff with all of those new options.

I still don't think any of that will make an audible difference.  But if you're playing with a mega-bucks optimized high end system and want to experiment then the options should be there.  The current single checkbox for playback from RAM is just a tease for those who want to go deeper.
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DoubtingThomas

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Re: Read from memory
« Reply #7 on: August 18, 2010, 06:07:03 am »

I play from memory because...  without it, when MC is started up on my  system, I get a short muting of sound shortly after playing the first track of the day.
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666JackTheKnife666

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Re: Read from memory
« Reply #8 on: August 19, 2010, 12:25:28 am »

I tested this feature with 14.0.155
The amount of memory MC allocates is limited to 256 Mb.
Indeed Win will use the pagefile if needed.
The answer is to disable the pagefile.
On a dedicated audio PC with sufficient memory you can do so without a problem.
At least mine is running this way.

ditto on the page file, with enough ram you don't need it.
I really really wish I could set the amount of ram that mc can use to preload audio for playback.
I have 8 Gig's of ram and would toss a gig to mc in a hart beat. is there a registry hack I could increase the buffer size anyone ?
Why do I want a large buffer? because I am a truck driver and on a semi the road pounds the hell out of computer equipment. If I could load an entire 8-10 hr audio book into ram and have my drives spin down into safe park mode I wouldn't have to buy new hard disks every 6mo to a year, good thing there cheap and I keep backups on dvdr's. Yes, I am looking forward to the day I can buy an affordable 1TB SSD, but ssd's are so damed expensive right now.  My current Media Library is sitting at 1.5 TB mostly audio books.
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Vincent Kars

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Re: Read from memory
« Reply #9 on: August 19, 2010, 06:53:31 am »

You can try a RAM disk, emulating a HD in memory
A USB hub plus a couple of thumbdrives might do the job too
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666JackTheKnife666

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Re: Read from memory
« Reply #10 on: August 19, 2010, 07:59:47 pm »

I have thought about the using a few flash drives & Ram Disks before and I can't seem to get around the problem of having MC load my selected playlist into the flash/Ram disk and play from there.
Ideally I would select a playlist hit play and mc would erase the flash/ram disk and copy everything in the playlist to my flash/ram disk then start playing from it.
I haven't figured out a way to make that happen.  Any ideas on how I might accomplish that ?
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HiFiTubes

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Re: Read from memory
« Reply #11 on: December 20, 2010, 07:53:18 am »

I have thought about the using a few flash drives & Ram Disks before and I can't seem to get around the problem of having MC load my selected playlist into the flash/Ram disk and play from there.
Ideally I would select a playlist hit play and mc would erase the flash/ram disk and copy everything in the playlist to my flash/ram disk then start playing from it.
I haven't figured out a way to make that happen.  Any ideas on how I might accomplish that ?

Any dev. on this front?
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