录制成WAV文件

Posted 2023-03-14

【中文标题】录制成WAV文件

【英文标题】：Record into WAV file

【发布时间】：2013-06-28 01:45:06

【问题描述】：

自从我发布this question 以来，我一直在尝试使用原始 PCM 数据自己编写一个有效的 WAV 文件。我已经设法编写了 FLAC 转换器（经过测试并且可以工作），但它不会对我一直在编写的 WAV 文件进行编码。

我不确定我做错了什么。我一直在网上搜索 other individuals source code 并将其与我自己的进行比较，但我仍然无法让它工作。

这里是精简的源代码（抱歉还是有点长，我自己记录到.wav需要一些代码）：

// Compile with "g++ test.ccp -o test -lasound"

// Use the newer ALSA API
#define ALSA_PCM_NEW_HW_PARAMS_API

#include <alsa/asoundlib.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>

struct WaveHeader

        char RIFF_marker[4];
        uint32_t file_size;
        char filetype_header[4];
        char format_marker[4];
        uint32_t data_header_length;
        uint16_t format_type;
        uint16_t number_of_channels;
        uint32_t sample_rate;
        uint32_t bytes_per_second;
        uint16_t bytes_per_frame;
        uint16_t bits_per_sample;
;

struct WaveHeader *genericWAVHeader(uint32_t sample_rate, uint16_t bit_depth, uint16_t channels)

    struct WaveHeader *hdr;
    hdr = (WaveHeader*) malloc(sizeof(*hdr));
    if (!hdr)
        return NULL;

    memcpy(&hdr->RIFF_marker, "RIFF", 4);
    memcpy(&hdr->filetype_header, "WAVE", 4);
    memcpy(&hdr->format_marker, "fmt ", 4);
    hdr->data_header_length = 16;
    hdr->format_type = 1;
    hdr->number_of_channels = channels;
    hdr->sample_rate = sample_rate;
    hdr->bytes_per_second = sample_rate * channels * bit_depth / 8;
    hdr->bytes_per_frame = channels * bit_depth / 8;
    hdr->bits_per_sample = bit_depth;

    return hdr;


int writeWAVHeader(int fd, struct WaveHeader *hdr)

    if (!hdr)
        return -1;

    write(fd, &hdr->RIFF_marker, 4);
    write(fd, &hdr->file_size, 4);
    write(fd, &hdr->filetype_header, 4);
    write(fd, &hdr->format_marker, 4);
    write(fd, &hdr->data_header_length, 4);
    write(fd, &hdr->format_type, 2);
    write(fd, &hdr->number_of_channels, 2);
    write(fd, &hdr->sample_rate, 4);
    write(fd, &hdr->bytes_per_second, 4);
    write(fd, &hdr->bytes_per_frame, 2);
    write(fd, &hdr->bits_per_sample, 2);
    write(fd, "data", 4);

    uint32_t data_size = hdr->file_size + 8 - 44;
    write(fd, &data_size, 4);

    return 0;


int recordWAV(const char *fileName, struct WaveHeader *hdr, uint32_t duration)

    int err;
    int size;
    snd_pcm_t *handle;
    snd_pcm_hw_params_t *params;
    unsigned int sampleRate = hdr->sample_rate;
    int dir;
    snd_pcm_uframes_t frames = 32;
    char *device = (char*) "plughw:1,0";
    char *buffer;
    int filedesc;

    printf("Capture device is %s\n", device);

    /* Open PCM device for recording (capture). */
    err = snd_pcm_open(&handle, device, SND_PCM_STREAM_CAPTURE, 0);
    if (err)
    
        fprintf(stderr, "Unable to open PCM device: %s\n", snd_strerror(err));
        return err;
    

    /* Allocate a hardware parameters object. */
    snd_pcm_hw_params_alloca(&params);

    /* Fill it in with default values. */
    snd_pcm_hw_params_any(handle, params);

    /* ### Set the desired hardware parameters. ### */

    /* Interleaved mode */
    err = snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
    if (err)
    
        fprintf(stderr, "Error setting interleaved mode: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    
    /* Signed 16-bit little-endian format */
    if (hdr->bits_per_sample == 16) err = snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
    else err = snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_U8);
    if (err)
    
        fprintf(stderr, "Error setting format: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    
    /* Two channels (stereo) */
    err = snd_pcm_hw_params_set_channels(handle, params, hdr->number_of_channels);
    if (err)
    
        fprintf(stderr, "Error setting channels: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    
    /* 44100 bits/second sampling rate (CD quality) */
    sampleRate = hdr->sample_rate;
    err = snd_pcm_hw_params_set_rate_near(handle, params, &sampleRate, &dir);
    if (err)
    
        fprintf(stderr, "Error setting sampling rate (%d): %s\n", sampleRate, snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    
    hdr->sample_rate = sampleRate;
    /* Set period size*/
    err = snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
    if (err)
    
        fprintf(stderr, "Error setting period size: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    
    /* Write the parameters to the driver */
    err = snd_pcm_hw_params(handle, params);
    if (err < 0)
    
        fprintf(stderr, "Unable to set HW parameters: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    

    /* Use a buffer large enough to hold one period */
    err = snd_pcm_hw_params_get_period_size(params, &frames, &dir);
    if (err)
    
        fprintf(stderr, "Error retrieving period size: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        return err;
    

    size = frames * hdr->bits_per_sample / 8 * hdr->number_of_channels; /* 2 bytes/sample, 2 channels */
    buffer = (char *) malloc(size);
    if (!buffer)
    
        fprintf(stdout, "Buffer error.\n");
        snd_pcm_close(handle);
        return -1;
    

    err = snd_pcm_hw_params_get_period_time(params, &sampleRate, &dir);
    if (err)
    
        fprintf(stderr, "Error retrieving period time: %s\n", snd_strerror(err));
        snd_pcm_close(handle);
        free(buffer);
        return err;
    

    uint32_t pcm_data_size = hdr->sample_rate * hdr->bytes_per_frame * duration / 1000;
    hdr->file_size = pcm_data_size + 44 - 8;

    filedesc = open(fileName, O_WRONLY | O_CREAT, 0644);
    err = writeWAVHeader(filedesc, hdr);
    if (err)
    
        fprintf(stderr, "Error writing .wav header.");
        snd_pcm_close(handle);
        free(buffer);
        close(filedesc);
        return err;
    
    fprintf(stdout, "Channels: %d\n", hdr->number_of_channels);
    for(int i = duration * 1000 / sampleRate; i > 0; i--)
    
        err = snd_pcm_readi(handle, buffer, frames);
        if (err == -EPIPE) fprintf(stderr, "Overrun occurred: %d\n", err);
        if (err) err = snd_pcm_recover(handle, err, 0);
        // Still an error, need to exit.
        if (err)
        
            fprintf(stderr, "Error occured while recording: %s\n", snd_strerror(err));
            snd_pcm_close(handle);
            free(buffer);
            close(filedesc);
            return err;
        
        write(filedesc, buffer, size);
    

    close(filedesc);
    snd_pcm_drain(handle);
    snd_pcm_close(handle);
    free(buffer);

    printf("Finished writing to %s\n", fileName);
    return 0;


int main(int argc, char *argv[]) 

    if(argc != 2)
    
        fprintf(stderr, "Usage: %s (record duration)\n", argv[0]);
        return -1;
    

    int err;
    struct WaveHeader *hdr;

    // Creates a temporary file in /tmp

    char wavFile[L_tmpnam + 5];
    char *tempFilenameStub = tmpnam(NULL);
    sprintf(wavFile, "%s.wav", tempFilenameStub);
    hdr = genericWAVHeader(44000, 16, 2);
    if (!hdr)
    
        fprintf(stderr, "Error allocating WAV header.\n");
        return -1;
    

    err = recordWAV(wavFile, hdr, 1000 * strtod(argv[1], NULL));
    if (err)
    
            fprintf(stderr, "Error recording WAV file: %d\n", err);
            return err;
    

    free(hdr);
    return 0;

程序运行时我得到的输出：

$ ./capture 5
Capture device is plughw:1,0
Channels: 2
Error occured while recording: Channel number out of range
Error recording WAV file: -44

有什么建议吗？我一直在努力解决这个问题。

【问题讨论】：

您确定设备支持立体声输入？

@BjornRoche 肯定的。此外，将上面程序中的频道更改为一个会产生相同的结果。

【参考方案1】：

试试这个：

printf("Channels: %d\n", hdr->number_of_channels);
for (i = 0; i < 2*16000/128; i++)

    printf("\n Recording %d",i);
    err = snd_pcm_readi(handle, buffer, frames);
    write(filedesc, buffer, size);
 

【参考方案2】：

snd_* 函数返回的错误代码是否定的。 有些函数可以返回一个正值来表示成功（例如，snd_pcm_readi 返回帧数）。

【讨论】：

但是返回值为-44？

即snd_pcm_recover的返回值。

好吧，这成功地得到了一个工作的 .wav 文件（+1），但它似乎仍然很早就被切断了。我想我会就此提出另一个问题并将其标记为已接受的答案。