HDMI sound intermittently drops out when loading a TZX from the Raspberry Pi 0.
HDMI sound intermittently drops out when loading a TZX from the Raspberry Pi 0.
Below is a breakdown of the issue and my findings on Sunday, February 14th, 2021.
I am using a ZX Spectrum Next Accelerated model (KS1, cased / complete unit).
All tests were perfomed using the "Neverending Story" TZX file (86,614 bytes) from worldofspectrum.org. It is the 2nd file listed (Original release - Perfect TZX TAP tape). I am always loading the game at 3.5Mhz (hitting Enter to default to Next mode) to listen to the audio as it loads. The original reason for this was to educate and inform how cassette tape loading was, in the 80s.
The core and O/S files were downloaded from this TBBLUE Gitlab repository and applied on Saturday, Feb 13th. The 3.01.08 core and OS 2.06N are present on the Next. The Rasperry Pi 0 is running the same software that shipped with the Next, as I have not yet opened her up. HDMI backpower from the (Samsung) TV to the Next was disabled (a long time ago) using a TV service menu option (this looks to have been successful as I haven't had cause to disconnect the HDMI cable since). The only peripheral connected is my M30 2.4g 8BitDo joypad - into the Joy 1 port. I use an inline power switch to turn the Next off and back on.
Step / Test performed / Result.
1 / Loaded TZX file (in Next personality and using the file browser - so I pair my joypad with the dongle in the Joy 1 port, select the TZX file using the browser then press 'B' on the joypad to load). / Confirmed HDMI audio drops out repeatedly while loading the TZX using the (same Analogue NT, 1m) HDMI cable I was using on Saturday.
2 / Entered REG 2,128 in BASIC to disable wi-fi module, returned to menu (no reset) and reloaded the TZX in the same way. / Saw no change to the audio drop outs. Added the REG command to my autoexec.bas to (without opening the unit and removing the ESP) eliminate the module from future tests.
3 / Loaded the same TZX file using the PC Spectrum emulator "Spectaculator". / Confirmed it is not the TZX file, there are no recorded audio fades or drop outs.
4 / Swapped to a 1M shielded cable (the fattest, stiffest, shortest HDMI cable I've come across). Reloaded the TZX the same as before. Whilst loading, I removed all (2) other HDMI device inputs to the TV. / Saw no change to the audio drop outs.
5 / Changed HDMI cable to a 2M shielded cable, reloaded. / Saw no change to the intermittent audio drop outs.
6 / Upon loading and leaving the game alone, I note that the game's music plays just fine with no A/V dropouts.
7 / I decided to load a .TAP version of "Neverending story". I turned "Tape loading simulation" on using the keyboard, then hit Enter to load the game in Next mode. / The game loads as expected - with no audio drop outs.
8 / I unplugged all the cables to the Next (this would be after turning it off first!), so everything (HDMI and power cable) except the joypad dongle / adapter, then plugged these cables back in. I plugged the 2 other HDMI cables I had removed (in step 4) from my TV back in (PS and TV box). I turned on my PlayStation and went through to its menu so as to leave it running. Going back to the Next (turning it back on), I loaded the TZX again with the same 2M shielded HDMI cable. / On loading this time, there were no audio drop outs (that I noticed). I noticed this time, I did not pair the joypad with the M30 joypad dongle (the dongle LED flashes when it is not paired) so I had used the keyboard to load the TZX.
9 / I turned the Next off and on again. Paired the joypad with the dongle. Reloaded the TZX. / The audio drops out again. I checked the Playstation was still turned on by changing the TV HDMI source (it was still on). Returning to the Next source, I saw the audio was still dropping out as the game was loading.
10 / I turned the Next off and removed the joypad dongle from the Next (so now I leave the joypad dongle removed), then reloaded the TZX. / The audio still drops out intermittently.
11 / I turned the Next off, unplugged the HDMI cable from the Next and plugged it in again, then turned the Next on and reloaded the TZX. / The audio still drops out.
At this point I felt that I had tried the obvious options available to try to pinpoint any external cause for the audio drop outs (that may be unique to me).
The problem only seems to manifest when loading a TZX file using the Pi 0, in that there are no audio drop outs when loading .TAP files.
If there are other ideas anyone might like to ask me to try, please get in touch, I'm happy to help where I can.
Hopefully the steps I've provided above can help in reproducing this issue.
Thanks.