question about burning and then reading (dd) to confirm sha256sum

[jd1008]

On 04/01/2015 08:24 PM, Robert Nichols wrote:
> On 04/01/2015 02:18 PM, jd1008 wrote:
>> After burning 3 DVD's, and reading them back to compute sha256sum.
>> all three of them generated these error messages during readback,
>> and all 3 messages show the error was past the 4gb offset.
>
> The DVDs will have some zero padding appended, and that will affect
> the SHA256 sums. You have to be careful not to read more bytes from
> the DVD than there are in the original ISO file.
>
Right, which is indeed how I try to compute a dvd's checksum.
At any rate, problem turned out to be the media, which is disappointing
because they are made by Sony, which I thought paid better attention
to the quality of production.