简介

该功能主要是用于测试音频模块的同源输出部分是否支持。

同源输出

分为软件和硬件两种模式，先来介绍一下同源输出的概念：简单地说就是往其中一个声卡写入数据，该声卡和另一个声卡都可以发出声音。一般情况下都是硬件实现，比较稳定，时延小。硬件的实现原理就是：当数据从应用写到DMAbuffer时，DMA会把数据同时传输到不同的声卡的DAI，以此实现同源输出，但是有个重要前提，播放通路的格式必须设置好一致，打开PCM流且打开DAMP开关。所以代码部分需要做的就是openPCM设置格式，不要close。软件方式的实现原理就比较简单粗暴，同时打开两个PCM流并同时写入，但是软件实现的话效果会差很多，而且很不稳定

使用方式

传入参数-h则是硬件实现，传入-s则是软件实现，在参数后面可以加上任意数量的文件名，因为改动后的tinyplay可以以数组的形式打开多个PCM流

代码

/* tinyplay.c
**
** Copyright 2011, The Android Open Source Project
**
** Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are met:
**     * Redistributions of source code must retain the above copyright
**       notice, this list of conditions and the following disclaimer.
**     * Redistributions in binary form must reproduce the above copyright
**       notice, this list of conditions and the following disclaimer in the
**       documentation and/or other materials provided with the distribution.
**     * Neither the name of The Android Open Source Project nor the names of
**       its contributors may be used to endorse or promote products derived
**       from this software without specific prior written permission.
**
** THIS SOFTWARE IS PROVIDED BY The Android Open Source Project ``AS IS'' AND
** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
** ARE DISCLAIMED. IN NO EVENT SHALL The Android Open Source Project BE LIABLE
** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
** SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
** DAMAGE.
*/#include <tinyalsa/asoundlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <signal.h>
#include <endian.h>#define ID_RIFF 0x46464952
#define ID_WAVE 0x45564157
#define ID_FMT  0x20746d66
#define ID_DATA 0x61746164struct riff_wave_header {uint32_t riff_id;uint32_t riff_sz;uint32_t wave_id;
};struct chunk_header {uint32_t id;uint32_t sz;
};struct chunk_fmt {uint16_t audio_format;uint16_t num_channels;uint32_t sample_rate;uint32_t byte_rate;uint16_t block_align;uint16_t bits_per_sample;
};static int close = 0;void play_sample_s(FILE *file, unsigned int *card, unsigned int device, unsigned int channels,unsigned int rate, unsigned int bits, unsigned int period_size,unsigned int period_count, uint32_t data_sz, int num);void play_sample_h(FILE *file, unsigned int *card, unsigned int device, unsigned int channels,unsigned int rate, unsigned int bits, unsigned int period_size,unsigned int period_count, uint32_t data_sz, int num);void stream_close(int sig)
{/* allow the stream to be closed gracefully */signal(sig, SIG_IGN);close = 1;
}int main(int argc, char **argv)
{FILE *file;struct riff_wave_header riff_wave_header;struct chunk_header chunk_header;struct chunk_fmt chunk_fmt;unsigned int device = 0;unsigned int card[5] = {-1,-1, -1, -1, -1};unsigned int period_size = 1024;unsigned int period_count = 4;char *filename;int more_chunks = 1;int s = 0, i = 0;if (argc < 2) {fprintf(stderr, "Usage: %s file.wav [-D card] [-d device] [-p period_size]"" [-n n_periods] \n", argv[0]);return 1;}filename = argv[1];file = fopen(filename, "rb");if (!file) {fprintf(stderr, "Unable to open file '%s'\n", filename);return 1;}fread(&riff_wave_header, sizeof(riff_wave_header), 1, file);if ((riff_wave_header.riff_id != ID_RIFF) ||(riff_wave_header.wave_id != ID_WAVE)) {fprintf(stderr, "Error: '%s' is not a riff/wave file\n", filename);fclose(file);return 1;}do {fread(&chunk_header, sizeof(chunk_header), 1, file);switch (chunk_header.id) {case ID_FMT:fread(&chunk_fmt, sizeof(chunk_fmt), 1, file);/* If the format header is larger, skip the rest */if (chunk_header.sz > sizeof(chunk_fmt))fseek(file, chunk_header.sz - sizeof(chunk_fmt), SEEK_CUR);break;case ID_DATA:/* Stop looking for chunks */more_chunks = 0;chunk_header.sz = le32toh(chunk_header.sz);break;default:/* Unknown chunk, skip bytes */fseek(file, chunk_header.sz, SEEK_CUR);}} while (more_chunks);/* parse command line arguments */argv += 2;while (*argv) {if (strcmp(*argv, "-d") == 0) {argv++;if (*argv)device = atoi(*argv);}if (strcmp(*argv, "-p") == 0) {argv++;if (*argv)period_size = atoi(*argv);}if (strcmp(*argv, "-n") == 0) {argv++;if (*argv)period_count = atoi(*argv);}if (strcmp(*argv, "-D") == 0) {argv++;do {card[i] = atoi(*argv);i++;argv++;} while (*argv && **argv != '-');}if (strcmp(*argv, "-s") == 0) {s = 1;}if (*argv)argv++;}if (s == 1)play_sample_s(file, card, device, chunk_fmt.num_channels, chunk_fmt.sample_rate,chunk_fmt.bits_per_sample, period_size, period_count, chunk_header.sz, i);elseplay_sample_h(file, card, device, chunk_fmt.num_channels, chunk_fmt.sample_rate,chunk_fmt.bits_per_sample, period_size, period_count, chunk_header.sz, i);fclose(file);return 0;
}int check_param(struct pcm_params *params, unsigned int param, unsigned int value,char *param_name, char *param_unit)
{unsigned int min;unsigned int max;int is_within_bounds = 1;min = pcm_params_get_min(params, param);if (value < min) {fprintf(stderr, "%s is %u%s, device only supports >= %u%s\n", param_name, value,param_unit, min, param_unit);is_within_bounds = 0;}max = pcm_params_get_max(params, param);if (value > max) {fprintf(stderr, "%s is %u%s, device only supports <= %u%s\n", param_name, value,param_unit, max, param_unit);is_within_bounds = 0;}return is_within_bounds;
}int sample_is_playable(unsigned int card, unsigned int device, unsigned int channels,unsigned int rate, unsigned int bits, unsigned int period_size,unsigned int period_count)
{struct pcm_params *params;int can_play;params = pcm_params_get(card, device, PCM_OUT);if (params == NULL) {fprintf(stderr, "Unable to open PCM device %u.\n", device);return 0;}can_play = check_param(params, PCM_PARAM_RATE, rate, "Sample rate", "Hz");can_play &= check_param(params, PCM_PARAM_CHANNELS, channels, "Sample", " channels");can_play &= check_param(params, PCM_PARAM_SAMPLE_BITS, bits, "Bitrate", " bits");can_play &= check_param(params, PCM_PARAM_PERIOD_SIZE, period_size, "Period size", " frames");can_play &= check_param(params, PCM_PARAM_PERIODS, period_count, "Period count", " periods");pcm_params_free(params);return can_play;
}void play_sample_s(FILE *file, unsigned int *card, unsigned int device, unsigned int channels,unsigned int rate, unsigned int bits, unsigned int period_size,unsigned int period_count, uint32_t data_sz, int num)
{struct pcm_config config;struct pcm *pcm[5];char *buffer;unsigned int size, read_sz;int num_read, i;memset(&config, 0, sizeof(config));config.channels = channels;config.rate = rate;config.period_size = period_size;config.period_count = period_count;if (bits == 32)config.format = PCM_FORMAT_S32_LE;else if (bits == 24)config.format = PCM_FORMAT_S24_3LE;else if (bits == 16)config.format = PCM_FORMAT_S16_LE;config.start_threshold = 0;config.stop_threshold = 0;config.silence_threshold = 0;for (i = 0; i < num; i++) {if (!sample_is_playable(card[i], device, channels, rate, bits, period_size, period_count)) {return;}pcm[i] = pcm_open(card[i], device, PCM_OUT, &config);if (!pcm[i] || !pcm_is_ready(pcm[i])) {fprintf(stderr, "Unable to open PCM device %u (%s)\n",device, pcm_get_error(pcm[i]));return;}}size = pcm_frames_to_bytes(pcm[0], pcm_get_buffer_size(pcm[0]));buffer = malloc(size);if (!buffer) {fprintf(stderr, "Unable to allocate %d bytes\n", size);free(buffer);for (i = 0; i < num; i++)pcm_close(pcm[0]);return;}printf("Playing sample: %u ch, %u hz, %u bit %u bytes\n", channels, rate, bits, data_sz);/* catch ctrl-c to shutdown cleanly */signal(SIGINT, stream_close);do {read_sz = size < data_sz ? size : data_sz;num_read = fread(buffer, 1, read_sz, file);if (num_read > 0) {for(i = 0; i < num; i++) {if (pcm_write(pcm[i], buffer, num_read)) {fprintf(stderr, "Error playing sample\n");break;}}data_sz -= num_read;}} while (!close && num_read > 0 && data_sz > 0);free(buffer);for (i = 0; i < num; i++)pcm_close(pcm[i]);
}void play_sample_h(FILE *file, unsigned int *card, unsigned int device, unsigned int channels,unsigned int rate, unsigned int bits, unsigned int period_size,unsigned int period_count, uint32_t data_sz, int num)
{struct pcm_config config;struct pcm *pcm[5];char *buffer;unsigned int size, read_sz;int num_read, i;memset(&config, 0, sizeof(config));config.channels = channels;config.rate = rate;config.period_size = period_size;config.period_count = period_count;if (bits == 32)config.format = PCM_FORMAT_S32_LE;else if (bits == 24)config.format = PCM_FORMAT_S24_3LE;else if (bits == 16)config.format = PCM_FORMAT_S16_LE;config.start_threshold = 0;config.stop_threshold = 0;config.silence_threshold = 0;for (i = 0; i < num; i++) {if (!sample_is_playable(card[i], device, channels, rate, bits, period_size, period_count)) {return;}pcm[i] = pcm_open(card[i], device, PCM_OUT, &config);if (!pcm[i] || !pcm_is_ready(pcm[i])) {fprintf(stderr, "Unable to open PCM device %u (%s)\n",device, pcm_get_error(pcm[i]));return;}}for (i = 1; i < num; i++)pcm_close(pcm[i]);size = pcm_frames_to_bytes(pcm[0], pcm_get_buffer_size(pcm[0]));buffer = malloc(size);if (!buffer) {fprintf(stderr, "Unable to allocate %d bytes\n", size);free(buffer);pcm_close(pcm[0]);return;}printf("Playing sample: %u ch, %u hz, %u bit %u bytes\n", channels, rate, bits, data_sz);/* catch ctrl-c to shutdown cleanly */signal(SIGINT, stream_close);do {read_sz = size < data_sz ? size : data_sz;num_read = fread(buffer, 1, read_sz, file);if (num_read > 0) {if (pcm_write(pcm[0], buffer, num_read)) {fprintf(stderr, "Error playing sample\n");break;}data_sz -= num_read;}} while (!close && num_read > 0 && data_sz > 0);free(buffer);pcm_close(pcm[0]);
}