ffmpeg+alsa 播放音频

#include "play.h" Play::Play(QObject *parent) : QObject(parent) { } int Play::snd_pcm_init() { snd_pcm_hw_params_t *hwparams = NULL; int ret; /* 打开PCM设备 */ ret = snd_pcm_open(&pcm, PCM_PLAYBACK_DEV, SND_PCM_STREAM_PLAYBACK, 0); if (0 > ret) { fprintf(stderr, "snd_pcm_open error: %s: %s\n", PCM_PLAYBACK_DEV, snd_strerror(ret)); return -1; } /* 实例化hwparams对象 */ snd_pcm_hw_params_malloc(&hwparams); /* 获取PCM设备当前硬件配置,对hwparams进行初始化 */ ret = snd_pcm_hw_params_any(pcm, hwparams); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_any error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } /************** 设置参数 ***************/ /* 设置访问类型: 交错模式 */ ret = snd_pcm_hw_params_set_access(pcm, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_access error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } /* 设置数据格式: 有符号16位、小端模式 */ ret = snd_pcm_hw_params_set_format(pcm, hwparams, SND_PCM_FORMAT_S16_LE); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_format error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } /* 设置采样率 */ ret = snd_pcm_hw_params_set_rate_near(pcm, hwparams, &wav_fmt.SampleRate, 0); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_rate error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } /* 设置声道数: 双声道 */ ret = snd_pcm_hw_params_set_channels(pcm, hwparams, wav_fmt.NumChannels); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_channels error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } snd_pcm_uframes_t frames_per_buffer = 0; snd_pcm_hw_params_get_buffer_size_max(hwparams, &frames_per_buffer); ret = snd_pcm_hw_params_set_buffer_size_near(pcm, hwparams, &frames_per_buffer); if(ret < 0) { qDebug() << "error"; } period_size = frames_per_buffer / periods; /* 设置周期大小: period_size */ //ret = snd_pcm_hw_params_set_period_size(pcm, hwparams, period_size, 0); ret = snd_pcm_hw_params_set_period_size_near(pcm, hwparams, &period_size, 0); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_period_size error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } #if 0 /* 设置周期数（驱动层buffer的大小）: periods */ ret = snd_pcm_hw_params_set_periods(pcm, hwparams, periods, 0); if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params_set_periods error: %s\n", snd_strerror(ret)); snd_pcm_hw_params_free(hwparams); //释放内存 snd_pcm_close(pcm); return -1; } #endif /* 使配置生效 */ ret = snd_pcm_hw_params(pcm, hwparams); snd_pcm_hw_params_free(hwparams); //释放hwparams对象占用的内存 if (0 > ret) { fprintf(stderr, "snd_pcm_hw_params error: %s\n", snd_strerror(ret)); snd_pcm_close(pcm); return -1; } snd_pcm_hw_params_get_period_size(hwparams,&period_size, 0); qDebug() << period_size << " " << frames_per_buffer; buf_bytes = period_size * wav_fmt.BlockAlign; //变量赋值，一个周期的字节大小 return 0; } int Play::open_wav_file(const char *file) { RIFF_t wav_riff; DATA_t wav_data; int ret; fd = open(file, O_RDONLY); if (0 > fd) { fprintf(stderr, "open error: %s: %s\n", file, strerror(errno)); return -1; } /* 读取RIFF chunk */ ret = read(fd, &wav_riff, sizeof(RIFF_t)); if (sizeof(RIFF_t) != ret) { if (0 > ret) perror("read error"); else fprintf(stderr, "check error: %s\n", file); close(fd); return -1; } if (strncmp("RIFF", wav_riff.ChunkID, 4) ||//校验 strncmp("WAVE", wav_riff.Format, 4)) { fprintf(stderr, "check error: %s\n", file); close(fd); return -1; } /* 读取sub-chunk-fmt */ ret = read(fd, &wav_fmt, sizeof(FMT_t)); if (sizeof(FMT_t) != ret) { if (0 > ret) perror("read error"); else fprintf(stderr, "check error: %s\n", file); close(fd); return -1; } if (strncmp("fmt ", wav_fmt.Subchunk1ID, 4)) {//校验 fprintf(stderr, "check error: %s\n", file); close(fd); return -1; } /* 打印音频文件的信息 */ printf("<<<<音频文件格式信息>>>>\n\n"); printf(" file name: %s\n", file); printf(" Subchunk1Size: %u\n", wav_fmt.Subchunk1Size); printf(" AudioFormat: %u\n", wav_fmt.AudioFormat); printf(" NumChannels: %u\n", wav_fmt.NumChannels); printf(" SampleRate: %u\n", wav_fmt.SampleRate); printf(" ByteRate: %u\n", wav_fmt.ByteRate); printf(" BlockAlign: %u\n", wav_fmt.BlockAlign); printf(" BitsPerSample: %u\n\n", wav_fmt.BitsPerSample); /* sub-chunk-data */ if (0 > lseek(fd, sizeof(RIFF_t) + 8 + wav_fmt.Subchunk1Size, SEEK_SET)) { perror("lseek error"); close(fd); return -1; } while(sizeof(DATA_t) == read(fd, &wav_data, sizeof(DATA_t))) { /* 找到sub-chunk-data */ if (!strncmp("data", wav_data.Subchunk2ID, 4))//校验 return 0; if (0 > lseek(fd, wav_data.Subchunk2Size, SEEK_CUR)) { perror("lseek error"); close(fd); return -1; } } fprintf(stderr, "check error: %s\n", file); return -1; } void Play::paly_wav(const char *file) { open_wav_file(file); snd_pcm_init(); int err; char *buf = (char *)malloc(buf_bytes); if (NULL == buf) { perror("malloc error"); close(fd); snd_pcm_close(pcm); return ; } unsigned long size = 0; while (1) { memset(buf, 0x00, buf_bytes); //buf清零 int ret = read(fd, buf, buf_bytes); //从音频文件中读取数据 if (0 >= ret) // 如果读取出错或文件读取完毕 { close(fd); //snd_pcm_drop(pcm); snd_pcm_drain(pcm); snd_pcm_close(pcm); if(ret != 0) { qDebug() << "error"; } break; } for(int i=0; i<ret; i++) { buf[i] *= 0.1; } size += ret; qDebug() << "size=" << size; ret = snd_pcm_writei(pcm, buf, period_size); if (ret < 0) { /* if ((err = snd_pcm_prepare (pcm)) < 0) { fprintf (stderr, "cannot prepare audio interface for use (%s)\n", snd_strerror (err)); close(fd); snd_pcm_close(pcm); return ; } else*/ { fprintf(stderr, "snd_pcm_writei error: %s %---d\n", snd_strerror(ret), ret); close(fd); snd_pcm_close(pcm); } return ; } else if (ret < period_size) { //实际写入的帧数小于指定的帧数 //此时我们需要调整下音频文件的读位置 //将读位置向后移动（往回移）(period_size-ret)*frame_bytes个字节