pali

> I didn't use a cdrom software for that image. It's directly from a physical disc! Ok! Also cdrom drive is free to return -EIO for some block of data....

Could you provide also output from `/usr/bin/cd_sessions /dev/sr0` for that physical cdrom image?

> I created another dd image with conv=noerror and it's now 35 MB in size. > [image-noerror_11MB_2-sessions.udf.gz](https://github.com/storaged-project/udisks/files/6029141/image-noerror_11MB_2-sessions.udf.gz) This image is unusable... it looks like that `dd` omitted empty blocks instead...

> Interesting, although I added files to the disc just once there's a third "virtual!?" session! I think this is because you have not closed disc yet, so this third...

Perfect, output from `cd_sessions` and file `image-ddrescue_11MB_2-sessions.udf.gz` seems to be usable! I will investigate it and let you know. What I have learnt today? Do not use `dd` but rather...

> Nevertheless, I can't reproduce the exact udisks behavior of the physical disc when using the ddrescue image. That is expected. Image itself does not contain session information. This is...

> `udfinfo: Warning: First and third Anchor Volume Descriptor Pointer not found, using second` And now I see where is the issue. Lets read first session: ``` $ ./udfinfo/udfinfo -b...

So I'm not surprised now that this udf multisession cd image cannot be detected, it is broken in a way that it is not valid udf image.

Anyway, seems that correct way to call `dd` is with arguments `conv=noerror,sync` (`noerror` is not enough, that `sync` should add required zero bytes). Can you just recheck if `dd conv=noerror,sync`...

> Yes, it's identical with the ddrescue image. Ok, so we should always call `dd` with arguments `conv=noerror,sync iflag=fullblock`. > [Test-Media-Mini_ddrescue.udf.gz](https://github.com/storaged-project/udisks/files/6030943/Test-Media-Mini_ddrescue.udf.gz) This image has same issue. And also has `impid=*UDF...