First commit
This player is not fully tested due to occasional drops on the output caused CRC errors when used with encoded audio such as Dolby E. However these drops have been observed with aplay when used in memory mapped mode so it is not believed to be an issue with this player. However, final testing is still outstanding
This commit is contained in:
James Cowdery
GitHub
parent
ba1305a0b9
commit
23c6888b6c
35
wavplay_am824/Makefile.Linux
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35
wavplay_am824/Makefile.Linux
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CFLAGS += -g
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CC = g++
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ARCH = Linux
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SRC = wavplay_am824.cpp
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HEADERS = am824_framer.h
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EXE = bin/$(ARCH)/wavplay_am824
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OBJ = bin/$(ARCH)/wavplay_am824.o
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LIBS = -lportaudio -lrt -lm -lsndfile -lasound -lpthread
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BIN = bin/$(ARCH)
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LD = g++
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LDFLAGS = -L/usr/local/lib -L/usr/lib/x86_64-linux-gnu -pthread -g
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all: $(BIN) $(EXE)
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$(BIN) :
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mkdir -p $(BIN)
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$(OBJ) : $(SRC) $(HEADERS)
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$(CC) -c $< -o $@ $(CFLAGS)
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$(EXE): $(OBJ) $(PALIB)
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$(LD) $(LDFLAGS) $(OBJ) $(LIBS) -o $@
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clean:
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rm -f bin/$(ARCH)/*
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297
wavplay_am824/am824_framer.h
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297
wavplay_am824/am824_framer.h
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/************************************************************************************************************
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* WavPlay AM824
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* Copyright (C) 2020, Dolby Laboratories Inc.
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>
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************************************************************************************************************/
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#include <stdint.h>
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#define CHANNEL_STATUS_BYTES 24
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#define WIDTH (8)
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#define BOTTOMBIT 1
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#define REFLECTED_POLYNOMIAL 0xb8 // Unreflected is 0x1d
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enum AM824ErrorCode{ AM824_ERR_OK = 0, AM824_ERR_BAD_SAMPLING_FREQUENCY = -1, AM824_ERR_UNSUPPORTED_BITDEPTH = -2 };
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enum AM824SamplingFrequency { FS_NOT_INDICATED = 0, FS_44100_HZ = 1, FS_48000_HZ = 2, FS_32000_HZ = 3 };
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enum AM824Endianess { AM824_BIG_ENDIAN, AM824_LITTLE_ENDIAN };
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class AM824Framer
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{
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uint8_t channelStatusIndex;
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uint8_t channelStatusMask;
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uint8_t channelStatus[CHANNEL_STATUS_BYTES];
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uint8_t subFrameCounter;
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uint8_t numChannels;
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uint8_t bitDepth;
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uint8_t crcTable[256];
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AM824Endianess endian;
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static uint8_t getParity(unsigned int n)
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{
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uint8_t parity = 0;
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while (n)
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{
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parity = 1 - parity;
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n = n & (n - 1);
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}
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return parity;
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}
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void crcTableInit(void)
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{
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uint8_t remainder;
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for (int dividend = 0; dividend < 256; ++dividend)
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{
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remainder = dividend << (WIDTH - 8);
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for (uint8_t bit = 0; bit < 8; bit++)
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{
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if (remainder & BOTTOMBIT)
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{
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remainder = (remainder >> 1) ^ REFLECTED_POLYNOMIAL;
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}
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else
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{
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remainder = (remainder >> 1);
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}
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}
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crcTable[dividend] = remainder;
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}
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}
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void setCRC(void)
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{
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uint8_t data;
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uint8_t remainder = 0xff;
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for (int byte = 0; byte < 23; byte++)
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{
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data = channelStatus[byte] ^ remainder;
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remainder = crcTable[data];
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}
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channelStatus[23] = remainder;
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}
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public:
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// Input number of channels and the bitdepth of the input samples
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// Note that the output bit depth is always 24 bit
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AM824Framer(uint8_t newNumChannels, /* Input - Number of channels of input/output audio */
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uint8_t newBitDepth, /* Input - Bit depth of input audio, output is always 32 bit */
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AM824Endianess outputEndianess, /* Input = Endianess of output samples, input is always machine order */
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AM824ErrorCode &err) /* Output - error code */
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{
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uint8_t i;
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channelStatusIndex = 0;
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channelStatusMask = 1;
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numChannels = newNumChannels;
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subFrameCounter = 0;
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bitDepth = newBitDepth;
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endian = outputEndianess;
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// Set certain channel status bits
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// Clear it first
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for (i = 0 ; i < CHANNEL_STATUS_BYTES ; i++)
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{
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channelStatus[i] = 0;
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}
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// Default Channel Status
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// Professional Bit
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channelStatus[0] |= 1;
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// Non-audio PCM
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channelStatus[0] |= 1 << 1;
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// 48kHz
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channelStatus[0] |= 2 << 6;
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switch(bitDepth)
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{
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case 16:
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channelStatus[2] |= 1 << 3;
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break;
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case 20:
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// Use of Auxillary bits
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channelStatus[2] |= 4;
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// 20 bit data
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channelStatus[2] |= 1 << 3;
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break;
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case 24:
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// Use of Auxillary bits
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channelStatus[2] |= 4;
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// 24 bit data
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channelStatus[2] |= 5 << 3;
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break;
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default:
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err = AM824_ERR_UNSUPPORTED_BITDEPTH;
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return;
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}
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crcTableInit();
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setCRC();
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err = AM824_ERR_OK;
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}
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AM824ErrorCode setSamplingFrequency(AM824SamplingFrequency fs_code)
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{
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if (fs_code > FS_32000_HZ)
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{
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return(AM824_ERR_BAD_SAMPLING_FREQUENCY);
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}
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// Reset top two bits and set accordingly
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channelStatus[0] &= 0x3f;
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channelStatus[0] |= fs_code << 6;
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setCRC();
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return(AM824_ERR_OK);
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}
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void setProfessionalMode(void)
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{
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channelStatus[0] |= 1;
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setCRC();
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}
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void setConsumerMode(void)
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{
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channelStatus[0] &= 0xfe;
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setCRC();
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}
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void setAudioMode(void)
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{
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channelStatus[0] &= 0xfd;
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setCRC();
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}
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void setDataMode(void)
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{
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channelStatus[0] |= 2;
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setCRC();
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}
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void getAM824Sample(uint32_t inputSample, uint8_t *outputBytes)
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{
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uint32_t outputSample;
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bool channelStatusBit = channelStatus[channelStatusIndex] & channelStatusMask;
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bool userBit = false;
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bool validityBit = false;
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// Input samples are MSB justified as per AES3
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if (bitDepth == 16)
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{
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outputSample = inputSample << 8;
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}
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else
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{
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outputSample = inputSample;
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}
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// Detect block start
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if ((channelStatusIndex == 0) && (channelStatusMask == 1))
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{
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outputSample |= 1 << 29;
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}
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// Detect frame start
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if (subFrameCounter == 0)
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{
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outputSample |= 1 << 28;
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}
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outputSample |= channelStatusBit << 26;
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outputSample |= userBit << 25;
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outputSample |= validityBit << 24;
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// Now complete except for parity so calculate that
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outputSample |= getParity(outputSample) << 27;
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// Now complete all the wraparound checks
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// Note that channel status chan be different for the different subframes (channels)
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// but in this example channel status is set to be the same for all subframes (channels)
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subFrameCounter++;
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if (subFrameCounter == numChannels)
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{
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subFrameCounter = 0;
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// Move to next channel status bit
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if (channelStatusMask == 0x80)
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{
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channelStatusMask = 1;
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channelStatusIndex++;
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if (channelStatusIndex == CHANNEL_STATUS_BYTES)
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{
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channelStatusIndex = 0;
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}
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}
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else
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{
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channelStatusMask = channelStatusMask << 1;
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}
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}
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if (endian == AM824_BIG_ENDIAN)
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{
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// Return in 32 bit Big Endian format
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*outputBytes++ = (outputSample & 0xff000000) >> 24;
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*outputBytes++ = (outputSample & 0x00ff0000) >> 16;
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*outputBytes++ = (outputSample & 0x0000ff00) >> 8;
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*outputBytes++ = (outputSample & 0x000000ff) >> 0;
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}
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else
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{
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// Return in 32 bit Little Endian format
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*outputBytes++ = (outputSample & 0x000000ff) >> 0;
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*outputBytes++ = (outputSample & 0x0000ff00) >> 8;
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*outputBytes++ = (outputSample & 0x00ff0000) >> 16;
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*outputBytes++ = (outputSample & 0xff000000) >> 24;
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}
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}
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/* Simple test code to check CRC implementation */
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/* See EBU Tech 3250 or AES3 for the reference for these examples */
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void testCRC(void)
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{
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unsigned int i;
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for (i = 0 ; i < CHANNEL_STATUS_BYTES ; i++)
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{
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channelStatus[i] = 0;
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}
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// From AES3-2-2009-r2019 - Example 1
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channelStatus[0] = 0x3d;
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channelStatus[1] = 2;
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channelStatus[4] = 2;
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setCRC();
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if (channelStatus[23] == 0x9b)
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{
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printf("Example 1 - passed\n");
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}
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else
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{
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printf("Example 1 - failed, expecting 0x9b, got 0x%x\n",channelStatus[23]);
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}
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channelStatus[0] = 0x01;
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channelStatus[1] = 0;
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channelStatus[4] = 0;
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setCRC();
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if (channelStatus[23] == 0x32)
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{
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printf("Example 2 - passed\n");
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}
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else
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{
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printf("Example 2 - failed, expecting 0x32, got 0x%x\n",channelStatus[23]);
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}
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}
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};
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