使用ffmpeg对pcm音频进行重采样(频率变换)的demo

#include "pcm_resample.h" int main2() { //初始化重采样参数 //音频重采样 上下文初始化 SwrContext *asc = NULL; //重采样上下文 AVFrame *pcm = NULL; //重采样输出空间 uint8_t *outs_new[2]; int inSamplerate = 48000, outSamplerate = 32000,ret = 0; AVSampleFormat inSamplefmt = AV_SAMPLE_FMT_S16; AVSampleFormat outSamplefmt = AV_SAMPLE_FMT_S16; int channels = 2; outs_new[0] = (uint8_t *)malloc(4096);//len 为4096 outs_new[1] = (uint8_t *)malloc(4096); asc = swr_alloc_set_opts(asc, av_get_default_channel_layout(channels), outSamplefmt, inSamplerate, av_get_default_channel_layout(channels), inSamplefmt, outSamplerate, 0, 0); if (!asc) { printf("swr_alloc_set_opts failed\n"); return -1; } ret = swr_init(asc); if (ret != 0) { printf("swr_init failed\n"); return -1; } printf("重采样初始化成功\n"); //重采样输出分配空间 pcm = av_frame_alloc(); pcm->format = outSamplefmt; pcm->channels = channels; pcm->channel_layout = av_get_default_channel_layout(channels); pcm->nb_samples = 1024; //一帧音频一通道的采样数量 ret = av_frame_get_buffer(pcm, 0);//给pcm分配存储空间 if (ret != 0) { printf("重采样分配输出空间失败\n"); return -1; } FILE *fb_in = fopen("in_data48Khz.pcm", "rb"); FILE *fb_out = fopen("out_data32Khz.pcm", "wb"); int nRead = 0, len_swr = 0; char indata1[4096] = {0}; //进行重采样数据 const uint8_t *indata[AV_NUM_DATA_POINTERS] = { 0 }; indata[0] = (const uint8_t*)indata1; int len = swr_convert(asc, outs_new, pcm->nb_samples, indata, pcm->nb_samples); pcm->data[0] = outs_new[0]; pcm->data[1] = outs_new[1]; while (1) { nRead = fread((void*)indata[0], 1, 4096, fb_in); if (nRead == 0) break; len_swr = swr_convert(asc, outs_new, pcm->nb_samples, (const uint8_t**)(&indata), pcm->nb_samples); printf("len_swr:%d\n", len_swr); fwrite(outs_new[0], 1, len_swr*4, fb_out); } if (pcm != NULL) { av_frame_free(&pcm); pcm = NULL; } if (asc != NULL) { swr_free(&asc); asc = NULL; } if (outs_new[1] != NULL) { free(outs_new[1]); outs_new[1] = NULL; } if (outs_new[0] != NULL) { free(outs_new[0]); outs_new[0] = NULL; } return 0; } /*函数名称:pcm_resample_init *函数功能：初始化pcm重采样参数 *传入参数：int insample:输入数据采样频率, int outsample:输出采样频率 *函数返回值：成功返回0，失败返回-1 *函数作者:吴豪乐 *日期：2021年1月5日 */ int pcm_resample::pcm_resample_init(int insample, int outsample) { //音频重采样 上下文初始化 inSamplerate = insample; outSamplerate = outsample; int ret = 0; inSamplefmt = AV_SAMPLE_FMT_S16; outSamplefmt = AV_SAMPLE_FMT_S16; channels = 2; dst_nb_channels = av_get_channel_layout_nb_channels(AV_CH_LAYOUT_STEREO); printf("dst_nb_channels:%d\n", dst_nb_channels); //outs_new[0] = (uint8_t *)malloc(4096);//len 为4096 //outs_new[1] = (uint8_t *)malloc(4096); asc = swr_alloc_set_opts(asc, av_get_default_channel_layout(channels), outSamplefmt, outSamplerate, av_get_default_channel_layout(channels), inSamplefmt, inSamplerate, 0, 0); if (!asc) { printf("swr_alloc_set_opts failed\n"); return -1; } #if 0 /* set options */ int64_t src_ch_layout = AV_CH_LAYOUT_STEREO, dst_ch_layout = AV_CH_LAYOUT_STEREO;//AV_CH_LAYOUT_SURROUND; av_opt_set_int(asc, "in_channel_layout", src_ch_layout, 0); av_opt_set_int(asc, "in_sample_rate", inSamplerate, 0); av_opt_set_sample_fmt(asc, "in_sample_fmt", inSamplefmt, 0); av_opt_set_int(asc, "out_channel_layout", dst_ch_layout, 0); av_opt_set_int(asc, "out_sample_rate", outSamplerate, 0); av_opt_set_sample_fmt(asc, "out_sample_fmt", outSamplefmt, 0); #endif ret = swr_init(asc); if (ret != 0) { printf("swr_init failed\n"); return -1; } indata[0] = (const uint8_t*)indata1; //重采样输出分配空间 pcm = av_frame_alloc(); pcm->format = outSamplefmt; pcm->channels = channels; pcm->channel_layout = av_get_default_channel_layout(channels); pcm->nb_samples = 1024; //一帧音频一通道的采样数量 ret = av_frame_get_buffer(pcm, 0);//给pcm分配存储空间 if (ret != 0) { printf("重采样分配输出空间失败\n"); return -1; } printf("pcm_resample_init 重采样初始化成功, inSamplerate:%d, outSamplerate:%d\n", inSamplerate, outSamplerate); src_nb_samples = 1024; //计算理论重采样后的数据量 /* compute the number of converted samples: buffering is avoided * ensuring that the output buffer will contain at least all the * converted input samples */ //e=av_rescale_rnd(a,b,c,d) => e=a*b/c max_dst_nb_samples = dst_nb_samples = av_rescale_rnd(src_nb_samples, outSamplerate, inSamplerate, AV_ROUND_UP);//这是按比例来求取的目标通道的采样数据:src_num/src_rate = dst_num/dst_rate => dst_num = src_num * dst_rate/src_rate printf("111max_dst_nb_samples:%d, dst_nb_samples:%d\n", max_dst_nb_samples, dst_nb_samples); //为重采样后的接收数据申请缓存 ret = av_samples_alloc_array_and_samples(&dst_data, &dst_linesize, 2, dst_nb_samples, outSamplefmt, 0); if (ret < 0) { printf("Could not allocate destination samples\n"); return -1; } return 0; } /*函数名称:pcm_resample_run *函数功能：开始进行重采样,每次重采样数据大小为4096字节 *传入参数：char *in_data：输入数据, int len_in：输入数据的大小(字节), char *out_data：输出数据, int len_out：输出数据的大小(字节) *函数返回值：成功返回0，失败返回-1 *函数作者:吴豪乐 *日期：2021年1月5日 */ int pcm_resample::pcm_resample_run(char *in_data, int len_in, char *out_data, int *len_out) { if (in_data == NULL || out_data == NULL || len_out == NULL) { printf("pcm_resample_run in_data or out_data error\n"); getchar(); return -1; } if (len_in < 4096) { printf("pcm_resample_run len_in or len_out error\n"); getchar(); return -1; } int ret = 0; //拷贝输入数据 memcpy(indata1, in_data, 4096); //计算实际重采样后得到的数据大小以及重新分配缓存 /* compute destination number of samples */ dst_nb_samples = av_rescale_rnd(swr_get_delay(asc, inSamplerate) + src_nb_samples, outSamplerate, inSamplerate, AV_ROUND_UP);//这里将重采样时间也计算进去的意思 if (dst_nb_samples > max_dst_nb_samples) { av_freep(&dst_data[0]); ret = av_samples_alloc(dst_data, &dst_linesize, 2, dst_nb_samples, outSamplefmt, 1); if (ret < 0) { printf("av_samples_alloc error\n"); return -1; } max_dst_nb_samples = dst_nb_samples; } printf("222max_dst_nb_samples:%d, dst_nb_samples:%d\n", max_dst_nb_samples, dst_nb_samples); int len_swr = 0; len_swr = swr_convert(asc, dst_data, dst_nb_samples, (const uint8_t**)(&indata), pcm->nb_samples); if (len_swr < 0) { printf("swr_convert error\n"); return -1; } dst_bufsize = av_samples_get_buffer_size(&dst_linesize, dst_nb_channels, len_swr, outSamplefmt, 1); if (dst_bufsize < 0) { printf("av_samples_get_buffer_size error\n"); return -1; } printf("dst_bufsize:%d, dst_nb_samples:%d, pcm->nb_samples：%d\n", dst_bufsize, dst_nb_samples, pcm->nb_samples); printf("outSamplerate:%d, inSamplerate:%d\n", outSamplerate, inSamplerate); //getchar(); *len_out = dst_bufsize; memcpy(out_data, dst_data[0], dst_bufsize); return 0; } /*函数名称:pcm_resample_release *函数功能：释放资源 *传入参数：无 *函数返回值：无 *函数作者:吴豪乐 *日期：2021年1月5日 */ void pcm_resample::pcm_resample_release(void) { if (pcm != NULL) { av_frame_free(&pcm); pcm = NULL; } if (asc != NULL) { swr_free(&asc); asc = NULL; } if (dst_data != NULL) { av_freep(&dst_data[0]); dst_data = NULL; } return; } pcm_resample::~pcm_resample() { pcm_resample_release(); } int main() { FILE *fb_in = fopen("in_data48Khz.pcm", "rb"); FILE *fb_out = fopen("out_data32Khz.pcm", "wb"); int nRead = 0, len_swr = 0; //初始化重采样 pcm_resample obj_pcm_resample; obj_pcm_resample.pcm_resample_init(48000, 32000); //进行重采样数据 char data_read[8192]