Audio recording on stock MSX systems

By snatchertas

Supporter (7)

snatchertas's picture

29-03-2018, 10:32

Greetings fellow MSX loyalists!

While looking around the Internet and MSX.ORG, I found that there is a complete absence of information regarding the audio/voice recording capabilities of the stock MSX machines.

I remember that my brother made a little sampling program on our Philips MSX2 (NMS 8245) that used up all available RAM and all the VideoRAM creating samples of 190kb (a minute or so of sampled music). I remember that we connected an Audio source in the TAPE input and the recording was of variable length, depending on the audio frequencies recorded.

All this time I thought that this was a very common feature but I found out that the only existing information on the subject (apart from whatever my brother remembers) is the existence of a program called MSX VOICE RECORDER by Sony. If anyone is interested in testing the program on real hardware, this program was included in the F1 tool disks of some Sony computers, but I also found it in the 2nd disk of Compile's DISK STATION #4.

Anyway, I will see what information my brother remembers and post them here but if anyone would like to chip in and cover this very little known aspect of our machines, let's see what we can come up with!

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By Manuel

Ascended (15600)

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29-03-2018, 14:29

Check also PSG sampler by Michel Shuqair.

By NYYRIKKI

Enlighted (5321)

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30-03-2018, 09:41

Indeed... this is not very common or well known feature. The problem with tape input is that it can input only 1bit wide voice sample. This means that the volume must be pretty high on tape player and still the output will be pretty poor quality. It is good enough that you can recognize what people say, but that's about it. This kind of sample technology was used in some games like "Oh shit" or "Laydock". The most popular way to play back such a sample is to use MSX "key click"-feature.

Although standard MSX is limited like this on input, it can play back better samples by using PSG. Most common way is to use 8bit samples as input and use lookup tables to transform that to PSG volumes. I believe this way of playback invaded MSX world from Atari ST, but it is not common either. No matter what kind of samples we talk about the problem is that they require huge amount of memory compared to what we are used to have. Very much later ARTRAG proved that MSX can play back even better quality samples... He used Viterbi-algorithm to convert a sample to PSG. The problem is that the sample creation takes HUGE amount of calculating power and storing it takes even more space than storing 8bit samples, but the playback can be done on any MSX and the playback quality is more close to CD audio that we are pretty much used to today on our PCs.

To solve the input problem MSX tR gave us a comparator circuit together with 8bit PCM output that can be used to input & output samples with reasonable quality. There are also other hardware solution made during the years, but none of those have gained much popularity in sampling... Phillips Music Module is anyway quite popular among users as a device. This extension is capable to input / output 8bit PCM and 4bit ADPCM samples.

By Grauw

Ascended (8310)

Grauw's picture

30-03-2018, 11:55

NYYRIKKI wrote:

Phillips Music Module is anyway quite popular among users as a device. This extension is capable to input / output 8bit PCM and 4bit ADPCM samples.

Actually it can do 10.3 floating point PCM, so an effective range of 18 bits. See Y8950 registers 15-17, allowing direct control over the MO output to the YM3014 DAC.

By ARTRAG

Enlighted (6229)

ARTRAG's picture

30-03-2018, 12:14

For speech there is also spectral approximation here
https://www.msx.org/forum/msx-talk/development/voice-synthes...
It works fine on psg and much better on scc