Quirk sending books to external card on Android tablet

[DMcCunney]

I have current 64 bit Calibre running under Win10 Pro. I use an Android tablet as my eBook viewer, and use Calibre to transfer books to the tablet. Connection is via a USB cable using mtp.

When Calibre is run and the tablet is plugged into the desktop, Calibre sees the tablet and enumerates the files already there. This takes a while, since there are thousands of books stored on an external 32GB microSD card. Eventually, Calibre finishes discovery, and books already on tablet are checked in the On Device column. Thus far, all is well.

The quirk occurs when I select new books to add to the tablet. When I try, Calibre sometimes says there isn't enough memory to hold them, but the card has GB of free space. Calibre is apparently trying to send the eBook files to Main memory. The problem is "Send to Card A" is already selected as the default destination for books Calibre will transfer. If I click on the Send to Device sub-menu and click the Send to Card A selection (which is already highlighted as the default), then try Sending to Device again, it works as expected.

What I don't understand is why it's failing the first time. Calibre has already been told Card A is the destination to send to, so why it tries to send to Main Memory at all is a good question. It's more confusing because it doesn't happen every time. I'm posting because it just happened today, and had happened yesterday as well, but had worked fine several days previous.

This is not a show stopper. It's easy enough to remind Calibre that Card A is the destination if I get the insufficient memory popup. I'd just love to know what's going on.

Suggestions?
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Dennis

[AnotherCat]

Originally Posted by DMcCunney

I have current 64 bit Calibre running under Win10 Pro. I use an Android tablet as my eBook viewer, and use Calibre to transfer books to the tablet. Connection is via a USB cable using mtp...

I use exactly the same with no problem.

Nothing comes immediately to mind as to what could be wrong except have you customized Calibre's MTP Device Interface plugin as to the folder the books should be sent to?

[DMcCunney]

Originally Posted by AnotherCat

I use exactly the same with no problem.

Nothing comes immediately to mind as to what could be wrong except have you customized Calibre's MTP Device Interface plugin as to the folder the books should be sent to?

I did say "Calibre has already been told Card A is the destination to send to", so yes.

As mentioned, this is not a showstopper - just a "WTF?" moment.

It's more WTF because it doesn't always happen. Transfer to device normally works as expected. I haven't thus far seen a pattern on when it doesn't work as expected.

Out of curiosity, what version of Android are you running? The tablet here has 4.4.2 Jellybean, and no upgrade is available for it. I don't normally care because Jellybean supports what I do and what apps I run. It's possible this is an Android side mtp quirk, that may not occur in a later version.
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Dennis

[theducks]

Is it possible that there is some other process that fires off when you connect the device?
A/V scan, sync...
Something that just slows the response a tiny bit!

[AnotherCat]

Originally Posted by DMcCunney

I did say "Calibre has already been told Card A is the destination to send to", so yes...

...Out of curiosity, what version of Android are you running?

Sorry, you have me confused now.

There is one place (maybe more) where one tells Calibre which of the main memory of the device or the card is the destination, and that is when one selects Send to Device.

Whereas Calibre's MTP Device Interface plugin that I referred to does not tell Calibre which of the main memory or card is the memory destination, it allows one to tell Calibre which folder you want books to go in when a book is sent to either the main memory or the card i.e. it does not define which of main memory or card is the destination.

Now I am only assuming that the MTP Device Plugin is implicated when sending a book to the tablet (seems a pretty sure bet though) and am not claiming that its customization is the problem, it is all that comes immediately to mind.

The version of Android on the tablet (Samsung) is 6.0.1.

[DMcCunney]

Originally Posted by theducks

Is it possible that there is some other process that fires off when you connect the device?
A/V scan, sync...
Something that just slows the response a tiny bit!

Not that I'm aware of.

Other background processes in Win10 might be culprits, but I pretty much know what those are and doubt they are factors.
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Dennis

[DMcCunney]

Originally Posted by AnotherCat

Sorry, you have me confused now.

There is one place (maybe more) where one tells Calibre which of the main memory of the device or the card is the destination, and that is when one selects Send to Device.

Calibre has already been told the target folder for eBooks is \eBooks on the card.

Whereas Calibre's MTP Device Interface plugin that I referred to does not tell Calibre which of the main memory or card is the memory destination, it allows one to tell Calibre which folder you want books to go in when a book is sent to either the main memory or the card i.e. it does not define which of main memory or card is the destination.

It doesn't define which is the destination by default, but does let you define which destination you want to be the default if you don't override it. Here, that's Card A. So clicking Send to Device should transfer books to \eBooks on Card A, and create sub directories as required for transferred volumes.

Normally, that's precisely what does happen, hence my confusion when it doesn't.

Now I am only assuming that the MTP Device Plugin is implicated when sending a book to the tablet (seems a pretty sure bet though) and am not claiming that its customization is the problem, it is all that comes immediately to mind.

The plugin is my first thought too.

The version of Android on the tablet (Samsung) is 6.0.1.

I have another tablet running 5.0 Lollipop. I haven't used it as eBook viewer in a while, but it's set up to do so with the same basic arrangement as the one I normally use. I'll test when I get a chance to see if Android version affects whether this happens.

Again, this is mostly "Why is this happening?" curiosity. It's not a big issue in usage.
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Dennis

[kovidgoyal]

Odd I can think of no way for that to happen. You want to debug this further you'll have to setup calibre to run from source and insert some print statements into the code at various points.

[DMcCunney]

Originally Posted by kovidgoyal

Odd I can think of no way for that to happen. You want to debug this further you'll have to setup calibre to run from source and insert some print statements into the code at various points.

It isn't worth that level of effort.

As mentioned, it's the work of a moment to get Calibre to try again when I get the spurious "not enough space on device" error, and it works as expected the second time.

But I can't think of a way for that to happen either, which is why my response is WTF?, and I posted a query here.
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Dennis