How do USB players keep track of position.

The devices that plug into the cigarette lighter and play sound from a USB drive through car radio speakers have the ability to remember where they left off, and, even when power is removed from them when the car is turned off, they restart from the start of the file or segment, often the start of a song, that had been playing when the car was turned off.

My question is, How does the device keep track of where to start up again. Is there a file written to the device that plugs into the cigarette lighter, or is it written to the USB drive? If to the device itself, will it look for a specific file name if a different USB drive is plugged in, or can it be fooled then into trying to play song 6, for example, on a different usb drive.

I could experiment to learn this stuff but I just don't have any time to do that before or during my upcoming car trip, and you might already know. Plus I wanted to tell you how great these things are if your car radio doesn't have a USB or 3.5mm input. See background.

Similar question about MP3 players. If one inputs to the car radio via the 3.5mm jack, it seems that the intermediate device can't keep track of anything, but the mp3 player can. Obviously, the information is stored in the MP3 player, but without my having to test, does anyone know if separate positions are kept for "music", "ebooks", and "podcasts"?. If so, that provides some versatility, and I could for example, put popular music in music, classical music in ebooks and broadway shows in podcasts. Or science podcasts in ebooks and history podcasts in podcasts.

Background: My 2005 Toyota seems to have been made just a year or two before it would have been possible to connect USB and 3.5mm inputs to its radio, using the CD changer or satellite port.

I wanted that because in that case the steering wheel controls would likely have controlled what was playing on a USB drive, and the song information would have displayed on the radio.

But since I couldn't have that, it turns out, except for the quality of the microphone (which might reflect more the acoustics of the car. The sound from the microphone is very intelligible, but my friend whom I called is good at being critical) the devices that plug into a cigarette lighter and communicate with RF do an amazing job. And they cost only about 16 to 22 dollars. One very compact one is only 11. I can give you specific urls if you want, but much of the difference is what will work best physically in your own car, depending on where the lighter is and what direction the opening points.

Other differences are whether they have a USB input, a USB charging port, a 3.5mm input, a TF input, a 1" square screen or less, and whether they will also connect with bluetooth to your cell phone. If they do the latter, they have a button that will answer the phone and hang up, and they use their own built-in microphone and the car radio speakers.

Reply to
micky
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replying to micky, Iggy wrote: All software outside of the USB, as far as I can tell...except the cell going to the car audio, that's wiring and such too. In 1-car I had a 3.5 plug and that always jumped back to the beginning of the drive, same on the PC when I took the drive back to add more.

But then, both my Radio Transmitter, in another car, and now in my new car leave off exactly where I unplugged or turned off, to the second and not to the beginning of the song. It's likely just live-logging the drive's cluster block or running an instant auto-save at the unplug/switch-off on just capacitor power.

Reply to
Iggy

The memory is in the car radio, not the USB device. Every time you power up the car radio, it checks some timestamp in the file system to see if there has been an update. If not, it knows where it was in the file. If it detects a change, it will rescan the whole USB device to find the new (or deleted) files. Also, I think if the battery on your car runs down, it will lose that info and have to rescan.

Jon

Reply to
Jon Elson

A USB player is a digital device (of course!). The music files on it are stored on a drive divided into sectors where small portions of data are stored. During playback, the player keeps track of which sector is being read, right up to the point the player is turned off. So, when you turn it back on, all the player needs to do is check which was the last sector read -- and resume playing from that point.

Reply to
J.Albert

Buford is what used to be called a juvenile delinquent.

But thanks to you and everyone else.

Reply to
micky

So it's in the player. I wonder if it could be fooled into playing the same sector in a different USB drive. I did switch back and forth when I had a rented car, but I didn't know the contents of the drives well enough to know if it was starting at the beginning of the second drive, or some place else.

For that matter, I used to use RadioMaximus to record 4 hours of The Big Broadcast every Sunday night, and so I wouldn't have to play a long segment from the beginning again if I turned the car off, I used its feature to record in 3 minutes segements. Everything was fine for weeks, but later, it would play the segments in a jumbled order. I don't know what changed. I also played the same program again and I couldn't recall if the jumbled order was the same the second time. (I was driving or I might have taken notes.)

I find it all very interesting.

Reply to
micky

So it's in the player. I wonder if it could be fooled into playing the same sector in a different USB drive. I did switch back and forth when I had a rented car, but I didn't know the contents of the drives well enough to know if it was starting at the beginning of the second drive, or some place else.

For that matter, I used to use RadioMaximus to record 4 hours of The Big Broadcast every Sunday night, and so I wouldn't have to play a long segment from the beginning again if I turned the car off, I used its feature to record in 3 minutes segements. Everything was fine for weeks, but later, it would play the segments in a jumbled order. I don't know what changed. I also played the same program again and I couldn't recall if the jumbled order was the same the second time. (I was driving or I might have taken notes.)

I find it all very interesting.

Reply to
micky

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