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Old 11-29-2007, 05:15 PM   #1
MaxOctane
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Default What does RDM on the radio mean?...

...because I thought it meant "random". Even when I push it, it says "Random disc play" or something like that, but my experience with RDM is as such...

I'm driving to work in the morning, and I decide to put my MP3 CD in the player. It has 135 MP3's on it and they are all in the ROOT directory! I hit RDM and listen to about 4 songs before I get to work. At lunch I go to the store and buy a present for my lovely wife whose birthday is on Monday. On the way there, I hear about 3 songs. Construction makes it longer to get there, so I only hear 2 songs on the way back.

So, I dust off the ol discrete math and combinatorics/permutations college book and go to town.

On the way to work, I heard 4 unique songs. On the way to the store, I heard one song which I heard on the way to work. On the way back from the store, I heard the same song again which I heard to work and to the store AND the second song I heard was a song I heard when going to the store!

This means I heard 9 songs total, and 6 unique songs. One song I heard 3 times, and another I heard 2 times.

First let's calculate the probability of listening to 9 unique songs in a row.

135/135*134/135*133/135... 127/135 = .76, so I have a 76% probability of hearing 9 unique songs in a row. I'd take those odds to Vegas any time.

Now, what is the probability that I listen to 9 songs, and hear the same one 3 times and the other 6 are unique out of a total set of 135 unique songs.

135/135*1/135*1/135*134/135*133/135...*129/135 = ~1/21,347 or .00468451% probability. Not quite sure I would take those odds with me to Vegas.

But, I heard the same song 3 times, and another song 2 times. What is the probability of hearing 1 song 3 times, another song 2 times, and the other 4 are unique songs.

135/135*1/135*1/135*134/135*1/134*133/135*132/135*131/135*130/135
which equals ~1/2,753,754 or .0000363141% probability.

What is the probability of listening to 9 songs and hearing AT LEAST 1 song 3 times?

p^n + C(n,1)*p^(n-1)*q + C(n,2)*p^(n-2)*q^2 + ... + C(n,r)*p^(r)*q^n-r) = probability that an event will happen at least r times in n trials. Using this equation, you get a probability of 1/30284.84

Now, It's been awhile since I've done this crap, so I could be wrong. If you decide to correct me, please do so tactfully. Regardless, my point is that the random seed that the GM Radio uses SUCKS!!!! I swear in a Cd full of 135 MP3's I'll hear the same song 8 or 9 times in just a few days. The chances of this being coincidence in practically nil as previously proven.

This makes me want to go to the dealer and ask to have the radio replaced, just to see the look on their face. Maybe if I record a dataset of several hundred songs and plot them on a scatter chart to support my argument. I wonder if they'll do it.
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Old 11-29-2007, 06:16 PM   #2
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I have the same problem with my iPod, and with the Archos iPod-like device I had before it.
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Old 11-29-2007, 06:22 PM   #3
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I have a headache now.Thank you very much!

Last edited by jesse12804; 11-29-2007 at 08:57 PM.
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Old 11-29-2007, 07:47 PM   #4
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Gray code??

BJK
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Old 11-29-2007, 08:20 PM   #5
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Old 11-29-2007, 08:45 PM   #6
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Quote:
Originally Posted by jesse12804 View Post
I have a headache now.Thanks you very much!

The challenge, can you summarize your question into one sentence?
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Old 11-29-2007, 08:54 PM   #7
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Old 11-29-2007, 08:55 PM   #8
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Quote:
Originally Posted by GaussianMist View Post

The challenge, can you summarize your question into one sentence?
How come the random "feature" of the radio does not randomize very well?

Last edited by SimonStern; 11-30-2007 at 10:38 AM.
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Old 11-29-2007, 09:10 PM   #9
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Although I didn't read your ENTIRE post I think I get the jist of it.

I've noticed on all my vehicle radios including the Corvette that random doesn't seem to really mean random. I don't know the reason...all I know is they're not very good at it. I seriously doubt that a new radio would make any difference.

I just randomize all my songs on the disk (I actually sort them alphabetically) and then just stick the CD in and listen away. With 200 or so songs on a CD and 6 CD's in my changer I don't have to worry about hearing a repeat for quite some time.
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Old 11-29-2007, 09:57 PM   #10
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Quote:
Originally Posted by SimonStern View Post
How come the random "feature" of the radio not randomize very well?
I'll check mine and report back.
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Old 11-29-2007, 09:58 PM   #11
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I never use random play for this reason.
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Old 11-29-2007, 10:32 PM   #12
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Quote:
Originally Posted by mwct View Post
I never use random play for this reason.


Actually, the radio does use a "random" scheme. If you consider the definition of "random" . . .

Quote:
lacking any definite plan or order or purpose; governed by or depending on chance
. . . it is doing exactly that.


The preferable scheme would be "random - do not repeat selections", but unfortunately, that is not a choice!
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Old 11-29-2007, 11:37 PM   #13
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My head hurts
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Old 11-29-2007, 11:40 PM   #14
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Quote:
Originally Posted by MaxOctane View Post
...because I thought it meant "random". Even when I push it, it says "Random disc play" or something like that, but my experience with RDM is as such...

I'm driving to work in the morning, and I decide to put my MP3 CD in the player. It has 135 MP3's on it and they are all in the ROOT directory! I hit RDM and listen to about 4 songs before I get to work. At lunch I go to the store and buy a present for my lovely wife whose birthday is on Monday. On the way there, I hear about 3 songs. Construction makes it longer to get there, so I only hear 2 songs on the way back.

So, I dust off the ol discrete math and combinatorics/permutations college book and go to town.

On the way to work, I heard 4 unique songs. On the way to the store, I heard one song which I heard on the way to work. On the way back from the store, I heard the same song again which I heard to work and to the store AND the second song I heard was a song I heard when going to the store!

This means I heard 9 songs total, and 6 unique songs. One song I heard 3 times, and another I heard 2 times.

First let's calculate the probability of listening to 9 unique songs in a row.

135/135*134/135*133/135... 127/135 = .76, so I have a 76% probability of hearing 9 unique songs in a row. I'd take those odds to Vegas any time.

Now, what is the probability that I listen to 9 songs, and hear the same one 3 times and the other 6 are unique out of a total set of 135 unique songs.

135/135*1/135*1/135*134/135*133/135...*129/135 = ~1/21,347 or .00468451% probability. Not quite sure I would take those odds with me to Vegas.

But, I heard the same song 3 times, and another song 2 times. What is the probability of hearing 1 song 3 times, another song 2 times, and the other 4 are unique songs.

135/135*1/135*1/135*134/135*1/134*133/135*132/135*131/135*130/135
which equals ~1/2,753,754 or .0000363141% probability.

What is the probability of listening to 9 songs and hearing AT LEAST 1 song 3 times?

p^n + C(n,1)*p^(n-1)*q + C(n,2)*p^(n-2)*q^2 + ... + C(n,r)*p^(r)*q^n-r) = probability that an event will happen at least r times in n trials. Using this equation, you get a probability of 1/30284.84

Now, It's been awhile since I've done this crap, so I could be wrong. If you decide to correct me, please do so tactfully. Regardless, my point is that the random seed that the GM Radio uses SUCKS!!!! I swear in a Cd full of 135 MP3's I'll hear the same song 8 or 9 times in just a few days. The chances of this being coincidence in practically nil as previously proven.

This makes me want to go to the dealer and ask to have the radio replaced, just to see the look on their face. Maybe if I record a dataset of several hundred songs and plot them on a scatter chart to support my argument. I wonder if they'll do it.
tell dealer all this and have them replace it..they will because they will be so embarrassed not understanding any of it!
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Old 11-29-2007, 11:44 PM   #15
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I have found similar "unrandomized" selections on a variety of CD players. Oh, by the way, the math lesson was humorous, but inaccurate for a car. The car's variables far outweigh any theoretical calculation. Have to figure a fudge factor for that! Back to the CD stuff. I often used to store songs in memory and then switching to random play, the various players somehow remembered these previously memorized songs in no particular order - but the same songs would eventually repeat over and over. I figured that the little computer chip figured that if the user liked these songs before, well then let's give them to him again and again even though he selected random play. See, somehow the chip learned and just wants to please you. Nothing's perfect!
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Old 11-30-2007, 01:25 AM   #16
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Quote:
Originally Posted by MaxOctane View Post
...because I thought it meant "random". Even when I push it, it says "Random disc play" or something like that, but my experience with RDM is as such...

I'm driving to work in the morning, and I decide to put my MP3 CD in the player. It has 135 MP3's on it and they are all in the ROOT directory! I hit RDM and listen to about 4 songs before I get to work. At lunch I go to the store and buy a present for my lovely wife whose birthday is on Monday. On the way there, I hear about 3 songs. Construction makes it longer to get there, so I only hear 2 songs on the way back.

So, I dust off the ol discrete math and combinatorics/permutations college book and go to town.

On the way to work, I heard 4 unique songs. On the way to the store, I heard one song which I heard on the way to work. On the way back from the store, I heard the same song again which I heard to work and to the store AND the second song I heard was a song I heard when going to the store!

This means I heard 9 songs total, and 6 unique songs. One song I heard 3 times, and another I heard 2 times.

First let's calculate the probability of listening to 9 unique songs in a row.

135/135*134/135*133/135... 127/135 = .76, so I have a 76% probability of hearing 9 unique songs in a row. I'd take those odds to Vegas any time.

Now, what is the probability that I listen to 9 songs, and hear the same one 3 times and the other 6 are unique out of a total set of 135 unique songs.

135/135*1/135*1/135*134/135*133/135...*129/135 = ~1/21,347 or .00468451% probability. Not quite sure I would take those odds with me to Vegas.

But, I heard the same song 3 times, and another song 2 times. What is the probability of hearing 1 song 3 times, another song 2 times, and the other 4 are unique songs.

135/135*1/135*1/135*134/135*1/134*133/135*132/135*131/135*130/135
which equals ~1/2,753,754 or .0000363141% probability.

What is the probability of listening to 9 songs and hearing AT LEAST 1 song 3 times?

p^n + C(n,1)*p^(n-1)*q + C(n,2)*p^(n-2)*q^2 + ... + C(n,r)*p^(r)*q^n-r) = probability that an event will happen at least r times in n trials. Using this equation, you get a probability of 1/30284.84

Now, It's been awhile since I've done this crap, so I could be wrong. If you decide to correct me, please do so tactfully. Regardless, my point is that the random seed that the GM Radio uses SUCKS!!!! I swear in a Cd full of 135 MP3's I'll hear the same song 8 or 9 times in just a few days. The chances of this being coincidence in practically nil as previously proven.

This makes me want to go to the dealer and ask to have the radio replaced, just to see the look on their face. Maybe if I record a dataset of several hundred songs and plot them on a scatter chart to support my argument. I wonder if they'll do it.
my 2005 radio did the same thing till GM replaced it.
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Old 11-30-2007, 01:42 AM   #17
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I have no idea what you are trying to say... I only have a college education... from the 70's. Pre "techie."

My response may have no significance to your question, but since I don't understand most of your question...

My C5 12 disc CD changer would truly randomly play any song from any of the twelve discs. Cadillac had the same system. Since then, I've noticed auto manufacturers (including Japan) have cheapened that functionality. "Random" means only on the disc that is in play... Not the other five or eleven. My last Toyota had a six disc player, but only randomly played a single disc. Same with my current 2005 Jeep with the premium audio.

Since GM has not come up with a sophisticated iPod link (see other posts on that), the only random an iPod can deliver is built into the iPod... "Shuffle."

Not a slam to you. Break it down to simple Corvette idiots like me, and maybe I'd have a better response
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Old 11-30-2007, 01:44 AM   #18
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I too need the Cliffs Notes version of this.
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Old 11-30-2007, 01:51 AM   #19
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You'd be amazed how often the same number comes up when you use randomizing code in a computer.
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Old 11-30-2007, 04:56 AM   #20
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They must be using that there fuzzy logic.

Having grown up listening to albums on turntables, I'm more used to hearing entire albums as opposed to random mixes. Some albums like the Moody Blues' Nights in White Satin or Pink Floyd's The Wall, just don't sound right when played out of order.
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Old 11-30-2007, 04:56 AM
 
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