#444 Spurious pulse at the beginning of a raw data block

[Alberto Garcia]

This shell line creates a simple TZX with a raw data block containing two full pulses:

echo -ne "ZXTape!\x1A\x01\x10\x15\x1E\x02\x00\x00\x08\x02\x00\x00\xf0\xf0"

Each bit is 542 tstates, so with the data contained in the last two bytes (1111000011110000) here is the expected output when read with libspectrum:

tstates: 2168, flags: level_high
tstates: 2168, flags: level_low
tstates: 2168, flags: level_high
tstates: 2168, flags: level_low
tstates: 0, flags: end-of-block, stop, end-of-tape

Here's the actual output:

tstates: 542, flags: level_low
tstates: 2168, flags: level_high
tstates: 2168, flags: level_low
tstates: 2168, flags: level_high
tstates: 2168, flags: level_high
tstates: 0, flags: end-of-block, stop, end-of-tape

There's two problems here:

1) The last pulse has the wrong level.
2) There's a spurious pulse at the beginning.

Problem 1 is making Fuse fail to load WAVs created from the tapes saved by the emulator, and it is dealt with in [bugs:#369].

Problem 2 can cause load failures depending on where the raw data block is located on the tape.

[Alberto Garcia]

This patch fixes the latter problem by correcting the initialization of raw data blocks.

[Alberto Garcia]

Note: there's one more bug with raw data blocks, and it's how libspectrum handles the value of "Used bits in last byte". This patch does not make it better, so I reported [bugs:#445] to deal with it.

In that bug report there's a patch and also a test case that exposes all the problems that I've found with raw data blocks in libspectrum.

[Sergio Baldoví]

I've tested this patch (isolated from the rest) with check_loaders (fuse-automation) and there isn't any variation with the expected results in 215 tapes. Doesn't seem to break anything.

[Alberto Garcia]

Thanks Sergio. Even if this particular patch doesn't break any test, this one should be applied together with the one in [bugs:#445].

[Sergio Baldoví]

Thanks. I meant isolated from [bugs:#431].

[Fredrick Meunier]

Thanks Berto!