hoglet67
commented
3 years ago @Hoglet Thanks in advance and also many more thx for this nice Project and wunderfull work.
FYI @IanSB is doing all the work now (and has been for at least a year),
I don't believe capturing audio on the Pi at the same time as capturing video is feaible. The memory timings are already incredibly tight, especially at higher bit depths.
There is also the issue of sample rate. As far as I understand, Paula supports variable sample rates (upto about 29KHz). HDMI audio needs to be at 48KHz. So a digital only solution would need sample rate conversion, which is not feasible in software (in the time we have available). It would also likely add significant lag.
(I have implemented a HDMI audio pipeline in the BBC Micro FPGA port for the Spectrum Next. Without proper sample rate conversion it sounds awful)
That leaves using an ADC to resample the analog audio, somehow feeding that into the Pi (I2S), and then encoding and muxing this into the HDMI stream. I just don't think there is the horse power to do this, without distrupting the video capture process. And it's unlikely to sound very good, as the ADC will be in a very noisy environment.
It's much easier just to take an analog audio cable from the Amiga to the monitor; most TVs support a seperate audio input. Or even better, use an external amplifier and speakers!
Unless @IanSB thinks otherwise, I think we should close this issue.
Dave
c0pperdragon
ZuiMelanieForno
Breeffeehey
IanSB
qbancoffee
Hello.
I came here from the Amiga-Digital-Video @c0pperdragon, where I made a Featurerequest.
The Issue over there, was reopened and I was sent here to do further "investigation". ;)
What is the situation?
There is a PCB what @c0pperdragon provides, und @IanSB are doing there some kind of Magic on the "Chip´s", to intercept digitaly RGB into the RPi Zero.
What I saw is that there are unused Pins, that could possibly be connected to another Signalsources. Like Audio, in form of digital Signals or maybe (not) amplified Analog Signals.
On the Amiga Side there are two differen Chip´s to do the Job. The one for the RGB is the Denise and the Audio is on the Paula-Chip (Pins 30 and 31, digital).
@c0pperdragon mentioned that maybe the "thight timing" wouldn´t allow to add another (asychron/synced) Signal into the RPi Zero?
I have not the "expertise" in E-Engineering or "Amiga-Chip-Stuff" at all, but if I understand it correctly, there could be a possibility to "mux-in" more to the HDMI-Output then it seems...
So my Issue or rather a Question is:
Can be different types of signals mixed into the HDMI, by muxing Audio into the HDMI-Data-Frames, for instance?
Maybe it could be achieved by using I²C or some AD/DA-Conversion IC´s as (drivers) additional Hardware for preprocessing (and if needed syncing) with the timing on the RPi Zero.
The Idea came from @Crushless to use I²C, so I dunno nothing about "Computahs"... ;)
@hoglet Thanks in advance and also many more thx for this nice Project and wunderfull work.
c.u Zui from Hamburg, Germany