jurjen.ladeniusandClaude Opus 4.8
f3340e86c6
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
238 lines
9.4 KiB
Plaintext
238 lines
9.4 KiB
Plaintext
=================================================================
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PCMENC - The Encoder for Crystal Clear PSG samples - Version 0.01
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=================================================================
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(c) 2006 Arturo Ragozini, Daniel Vik
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Introduction
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------------
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This package contains an encoder application and replayers to create
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and play crystal clear PSG samples on your MSX.
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Each input sample is approximated by the sum of 3 PSG channels. As the
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z80 can vary only one channel at time, the encoder, using a Viterbi
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search, finds the best sequence of PSG channel variations that
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approximate
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(MSE) the input sequence. The output of pcmenc is a sequence of PSG
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levels for the 3 channels that best approximate the input sequence.
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Provided that the ASM replayer can change the PSG levels at a fixed
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rate, you can configure the encoder at least in 3 ways:
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1) spending three PSG transitions per sample in input: this leads to the
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best SNR (the lowest quantization noise) but limits the sampling
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frequency to 11,025kHz. The unpacked encoding rate is 3x4=12bit per
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sample.
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2) spending two PSG transitions per input sample: you have average SNR
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and you can rise the sampling frequency up to 22,050kHz. The unpacked
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encoding rate is 3x4/2=6bit per sample.
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3) one PSG transition per input sample: minimum quality in exchange of
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maximum sampling frequency. Using the provided replayer you can reach
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44100kHz. The unpacked encoding rate is 4bits per sample.
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Moreover the encoder (and the replayers), supports multiple types of
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packing. By default, the he PSG levels are RLE packed and can be
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optionally segmented in chunks in order to be used applications that use
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multiple memory pages.
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Although pcmenc.exe is able to do frequency conversions (upsampling and
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downsampling), its suggested to use a 8bit (or 16bit) mono source wave
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with the same frequency as the replayer frequency. In this case no
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frequency conversion occurs. To get good results some preprocessing of
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the wave file may be required.
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Usage of pcmenc.exe
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-------------------
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Usage:
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pcmenc.exe [-r] [-e <encoding>] [-cpuf <freq>] [-p <packing>]
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[-dt1 <tstates>] [-dt2 <tstates>] [-dt3 <tstates>]
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[-a <amplitude>] [-rto <ratio>] <wavfile>
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-r Pack encoded wave into 8kB blocks for rom replayers
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-p <packing> Packing type: b7...b5|b4...b0
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0 = 4bit RLE (default) run len|PSG vol
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1 = 3 bit RLE; as before but b5 =0
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1 = 1 byte vol
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2 = 1 byte {ch, vol} pairs
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-cpuf <freq> CPU frequency of the CPU (Hz)
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Default: 3579545
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-dt1 <tstates> CPU Cycles between update of channel A and B
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-dt2 <tstates> CPU Cycles between update of channel B and C
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-dt3 <tstates> CPU Cycles between update of channel C and A
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The replayer sampling base period is
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T = dt1+dt2+dt3
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Defaults (depends on rto):
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ratio = 1 : dt1=32, dt2=27, dt3=266 => 11014Hz
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ratio = 2 : dt1=156,dt2=27, dt3=141 => 22096Hz
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ratio = 3 : dt1=73, dt2=84, dt3=87 => 44011Hz
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Note that the replayed sampling base period depends
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on the replayer and how many samples it will play
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in each PSG tripplet update. The default settings
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are based on:
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1 : replayer_core11025 which plays one sample per
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psg tripplet update
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2 : replayer_core22050 which plays two sample per
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psg tripplet update
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3 : replayer_core44100 which plays three sample
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per psg tripplet update
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-a <amplitude> Input amplitude before encoding.
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Default 115
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-rto <ratio> Number of input samples per PSG triplet
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Default: 1
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This parameter can be used to oversample the input
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wave. Note that this parameter also will affect the
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replay rate based on how many samples per PSG tripplet
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update the replayer uses.
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-c <costfun> Viterbi cost function:
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1 : ABS measure
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2 : Standard MSE (default)
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> 2 : Lagrange interpolation of order 'c'
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-i <interpol> Resampling interpolation mode:
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0 = Linear interpolation
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1 = Quadratic interpolation
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2 = Lagrange interpolation (default)
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<wavfile> Filename of .wav file to encode
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The values of dt1, dt2, and dt3 defines the time (in T-states) between
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the PSG channel updates in the replayer. The sum of the dt’s values is
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the base sample period of the replayer. You can fit one, two, or three
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PSG transitions per inputs sample depending on the ratio between the
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frequency input and the replayer base frequency. The frequency of the
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replayer is:
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CPU frequency
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replayed frequency = ---------------
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dt1 + dt2 + dt3
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The default values are chosen to match the replayer for the specific
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encoding that comes with the pcmenc package and the frequency of the
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replayed samples is by default either 11.025Hz, 22.05Hz or 44.1Hz but
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this can be controlled by the dt arguments.
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Ratio 1 - One input sample per PSG output triplet
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Each sample in input is approximated by 3 PSG transitions: this solution
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gives the best SNR as the PSG can vary its 3 channels each sample in
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input (human voice, low pass sounds and bass music it can reach 42dB of
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SNR). On a standard MSX the sampling frequency cannot be much higher
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than 8KHz,moreover each samples needs 12bit to be stored, do not expect
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miracles from RLE.
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Ratio 2 - Two input sample per PSG output triplet
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Each couple of samples in input is approximated by 3 PSG transitions:
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this
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solution has lower SNR, as for odd samples the PSG can vary 2 channels
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while on even samples the PSG vary the last channel (for "well
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behavioured" inputs you can have 36dB of SNR). On a standard MSX the
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sampling frequency cannot be much higher than 22kHz. Each samples needs
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6bit to be stored, as usual, do not expect miracles from RLE.
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Ratio 3 - Three input sample per PSG output tripplet
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Each samples in input is approximated by 1 PSG transitions: this
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solution has the lowest SNR (for "well behavioured" inputs you can have
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26dB of SNR) but, on a standard MSX, the sampling frequency can rise up
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to 44kHz.
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Each samples needs 4bit to be stored and as usual, do not expect
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miracles from RLE. Due to the special time constraints the replayer that
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can support 44kHz requires 3bit RLE (instead of the 4bit RLE).
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Ratio > 3 - Oversampled input
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A ratio > 3 will result in an oversampled input. In these cases, the
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ratio should be a multiple of the desired input sample per PSG output
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tripplet. When using a ratio > 3, the dt1, dt2, and dt3 values needs
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to be set in the argument list.
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To get the best result its good to have an input wave file to the
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encoder that matches the replayed frequency. The encoder does down and
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upsampling of the input wave to match the replayed frequency, but the
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current implementation does not do antialiasing which most likely is
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needed to get a good result. So the recommended process is:
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1. Find a wave file you'd like to have played on the MSX
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2. Downsample it to the desired playback frequency, e.g. 11kHz with
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antialiasing
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(i.e. a 5.5kHz lowpass filter)
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3. Run the encoder with the downsampled wave file as input.
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4. Change the incbin statement in vplayer.asm to the filename of the
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generated .bin file.
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5. Assemble vplayer.asm with sjasm (or other compatible assembler)
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6. Run the generated .com or .rom file in your MSX
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Examples for creating .com readable samples with pcmenc.exe
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-----------------------------------------------------------
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The replayer cores show the preferred command line options to be used
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by the replayer you wish to use.
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To encode a file for the .com version of the replayer:
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PcmEnc.exe sample.wav
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This outputs a file called sample.bin which can be compiled with
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vplayer.asm:
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sjasm vplayer.asm
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The ExeType in vplayer.asm should be set to 0 to create a .com file.
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The com file can then be loaded and played in your MSX. Note that this
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replayer is only able to play short samples that fits in 64kB ram.
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Examples for creating ascii8 .rom readable samples with pcmenc.exe
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------------------------------------------------------------------
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To encode a file for the .com version of the replayer:
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PcmEnc.exe -r sample.wav
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The -r option will split the sample data into 8kB blocks to make it
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playable with the rom version of the replayer (not provided). The
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output is a file called sample.bin which can be compiled with
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vplayer.asm:
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sjasm vplayer.asm
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The ExeType should be set to 0 to create an ascii8 .rom file.
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The com file can then be loaded into a flash cart, ESE ram, MEGA ram (or
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equivalent) and played on your MSX.
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Compiling pcmenc.exe:
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---------------------
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To compile pcmenc.exe using gnu gxx, type:
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gxx pcmenc.cpp resample.c -o pcmenc.exe -O2 -Wall
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or:
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g++ pcmenc.cpp resample.c -o pcmenc.exe -O2 -Wall
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The encoder is only tested on little endian machines but is prepared to
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be compiled on big endian machines as well.
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