How do USB players keep track of position.

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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.



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Re: How do USB players keep track of position.
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.
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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.

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for full context, visit https://www.homeownershub.com/maintenance/how-do-usb-players-keep-track-of-position-1149479-.htm
 



Re: How do USB players keep track of position.
micky wrote:

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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

Re: How do USB players keep track of position.
In rec.autos.tech, on Thu, 02 Nov 2017 12:18:24 -0700, mike

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Buford is what used to be called a juvenile delinquent.  

But thanks to you and everyone else.  

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How do USB players keep track of position.
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if they are programmed specifically to do so.

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if they are programmed specifically to do so.

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they are programmed specifically to do so.

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There is hardware allowing both to be programmed for that purpose  

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Computer viruses can sometimes re-program a USB or other device to suit its purposes. For example, notice that font types, sounds or colors may change seemingly for no reason.

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