请教下，每隔1秒， av_read_frame(fmt_ctx, &pkt)返回-35，录制的音频无法播放，可能什么原因呢？

Question

代码如下：

#include "testc.h"

void rec_audio(){
    int ret = 0;
    char errors[1024] = {0, };
    
    // ctx
    AVFormatContext *fmt_ctx = NULL; // init NULL
    AVDictionary *options = NULL;
    
    // packet
    int count = 0;
    AVPacket pkt;
    av_init_packet(&pkt);
    
    // [[video device]:[audio device]]
    char *devicename = ":0";
    
    // set log level
    av_log_set_level(AV_LOG_DEBUG);
    
    // register audio device
    avdevice_register_all();
    
    // get format
    AVInputFormat *iformat = av_find_input_format("avfoundation");
    
    // open device
    if ((ret = avformat_open_input(&fmt_ctx, devicename, iformat, &options)) < 0) {
        av_strerror(ret, errors, 1024);
        fprintf(stderr, "Failed to open audio device, [%d]%s\n", ret, errors);
        return;
    }
    
    // create file
    char *out = "/Users/wanghe/project/audio.pcm";
    FILE *outfile = fopen(out, "wb+");
    
    // read data from device
    while (count++ < 20) {
        ret = av_read_frame(fmt_ctx, &pkt);
        // device not ready, sleep 1s
        if (ret == -35) {
            av_log(NULL, AV_LOG_WARNING, "device not ready, wait 1s\n");
            sleep(1);
            continue;
        }
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "read data error from device\n");
            break;
        }
        av_log(NULL, AV_LOG_INFO,
               "pkt size is %d(%p),count=%d \n",
                pkt.size, pkt.data, count);
        
        // write file
        fwrite(pkt.data, pkt.size, 1, outfile);
        fflush(outfile);
        av_packet_unref(&pkt);
        }
//    close file
    fclose(outfile);
    // close device and release ctx
    avformat_close_input(&fmt_ctx);
    av_log(NULL, AV_LOG_DEBUG, "finish!\n");
    return;
}

以下是点击button输出的日志

[avfoundation @ 0x7fdf2b90e140] audio device '内建麦克风' opened
device not ready, wait 1s
pkt size is 4096(0x7fdf2b102800),count=2 
device not ready, wait 1s
pkt size is 4096(0x7fdf2b102000),count=4 
device not ready, wait 1s
pkt size is 4096(0x7fdf2c09ae00),count=6 
device not ready, wait 1s
pkt size is 4096(0x7fdf2b102000),count=8 
device not ready, wait 1s
pkt size is 4096(0x7fdf2c09ae00),count=10 
device not ready, wait 1s
pkt size is 4096(0x7fdf2b102000),count=12 
device not ready, wait 1s
pkt size is 4096(0x7fdf2c8b3c00),count=14 
device not ready, wait 1s
pkt size is 4096(0x7fdf2c8b3c00),count=16 
device not ready, wait 1s
pkt size is 4096(0x7fdf2a85f800),count=18 
device not ready, wait 1s
pkt size is 4096(0x7fdf2c813a00),count=20 
finish!

麻烦老师帮忙分析下可能的原因，难道是麦克风被其它应用占用了。

Answer 1

提问者 戴着眼镜的平头哥 2023-06-10 20:12:01

解决了，把sleep换成usleep(100); 然后count++ < 500

全部代码如下

#include "testc.h"

void rec_audio(){
    int ret = 0;
    char errors[1024] = {0, };
    
    // ctx
    AVFormatContext *fmt_ctx = NULL; // init NULL
    AVDictionary *options = NULL;
    
    // packet
    int count = 0;
    AVPacket pkt;
    av_init_packet(&pkt);
    
    // [[video device]:[audio device]]
    char *devicename = ":0";
    
    // set log level
    av_log_set_level(AV_LOG_DEBUG);
    
    // register audio device
    avdevice_register_all();
    
    // get format
    AVInputFormat *iformat = av_find_input_format("avfoundation");
    
    // open device
    if ((ret = avformat_open_input(&fmt_ctx, devicename, iformat, &options)) < 0) {
        av_strerror(ret, errors, 1024);
        fprintf(stderr, "Failed to open audio device, [%d]%s\n", ret, errors);
        return;
    }
    
    // create file
    char *out = "/Users/wanghe/project/audio.pcm";
    FILE *outfile = fopen(out, "wb+");
    // read data from device
    while (count++ < 50000) {
        ret = av_read_frame(fmt_ctx, &pkt);
        // device not ready, sleep 1s
        if (ret == -35) {
            av_log(NULL, AV_LOG_WARNING, "device not ready, wait 1s\n");
            av_packet_unref(&pkt);
            usleep(100);
            continue;
        }
        if (ret < 0) {
            av_log(NULL, AV_LOG_ERROR, "read data error from device\n");
            av_packet_unref(&pkt);
            break;
        }
        av_log(NULL, AV_LOG_INFO,
               "pkt size is %d(%p),count=%d \n",
                pkt.size, pkt.data, count);
        
        // write file
        fwrite(pkt.data, pkt.size, 1, outfile);
        fflush(outfile);
        av_packet_unref(&pkt);
        }
//    close file
    fclose(outfile);
    // close device and release ctx
    avformat_close_input(&fmt_ctx);
    av_log(NULL, AV_LOG_DEBUG, "finish!\n");
    return;
}