在我之前的问题here中，我设法将一个有效的.wav文件作为输出。但是，当我将这个.wav文件放入我的编码器（使用其他.wav文件进行测试并且工作正常）时，我的编码器会在它完成之前向我发回错误。
这是我的输出：
$ ./capture 2
Capture device is plughw:1,0
Finished writing to /tmp/filevXDDX6.wav
Starting encode to /tmp/filevXDDX6.flac
Wrote 3641 bytes, 4096/88200 samples, 2/22 frames
Wrote 6132 bytes, 8192/88200 samples, 2/22 frames
Wrote 8748 bytes, 12288/88200 samples, 3/22 frames
Wrote 11253 bytes, 16384/88200 samples, 4/22 frames
Wrote 13697 bytes, 20480/88200 samples, 5/22 frames
Wrote 16222 bytes, 24576/88200 samples, 6/22 frames
Wrote 18811 bytes, 28672/88200 samples, 7/22 frames
Wrote 21900 bytes, 32768/88200 samples, 8/22 frames
Wrote 24681 bytes, 36864/88200 samples, 9/22 frames
Wrote 27408 bytes, 40960/88200 samples, 10/22 frames
Wrote 30494 bytes, 45056/88200 samples, 11/22 frames
Wrote 34107 bytes, 49152/88200 samples, 12/22 frames
Wrote 37447 bytes, 53248/88200 samples, 13/22 frames
Wrote 40719 bytes, 57344/88200 samples, 14/22 frames
Wrote 45257 bytes, 61440/88200 samples, 15/22 frames
Wrote 48735 bytes, 65536/88200 samples, 16/22 frames
Wrote 52842 bytes, 69632/88200 samples, 17/22 frames
Wrote 56529 bytes, 73728/88200 samples, 18/22 frames
Wrote 60185 bytes, 77824/88200 samples, 19/22 frames
Wrote 63906 bytes, 81920/88200 samples, 20/22 frames
ERROR: reading from WAVE file
Wrote 67687 bytes, 86016/88200 samples, 21/22 frames
Encoding: FAILED
State: FLAC__STREAM_ENCODER_UNINITIALIZED
我不确定为什么它会提前切断，但我很确定它与我如何记录自己的.wav文件有关（因为我的编码器可以正常使用其他文件）
这是我的代码（抱歉有点长，我尽可能减少）：
// 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(¶ms);
/* 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 < 0) err = snd_pcm_recover(handle, err, 0);
// Still an error, need to exit.
if (err < 0)
{
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;
}
有什么建议吗？
修改 - 我被告知要将.wav文件的标头与arecord生成的标头进行比较。结果如下：
$ stat -c %s arecord.wav
352844
$ stat -c %s /tmp/filevXDDX6.wav
345004
$ xxd -g1 arecord.wav | head
0000000: 52 49 46 46 44 62 05 00 57 41 56 45 66 6d 74 20 RIFFDb..WAVEfmt
0000010: 10 00 00 00 01 00 02 00 44 ac 00 00 10 b1 02 00 ........D.......
0000020: 04 00 10 00 64 61 74 61 20 62 05 00 08 00 08 00 ....data b......
0000030: 08 00 08 00 07 00 07 00 fe ff fe ff f7 ff f7 ff ................
0000040: f6 ff f6 ff ee ff ee ff ee ff ee ff f6 ff f6 ff ................
0000050: f0 ff f0 ff e7 ff e7 ff ee ff ee ff f4 ff f4 ff ................
0000060: f4 ff f4 ff f7 ff f7 ff fe ff fe ff fc ff fc ff ................
0000070: fa ff fa ff f5 ff f5 ff ed ff ed ff ee ff ee ff ................
0000080: f8 ff f8 ff f4 ff f4 ff ed ff ed ff ee ff ee ff ................
0000090: f8 ff f8 ff f6 ff f6 ff f0 ff f0 ff ee ff ee ff ................
$ xxd -g1 /tmp/filevXDDX6.wav | head
0000000: 52 49 46 46 44 62 05 00 57 41 56 45 66 6d 74 20 RIFFDb..WAVEfmt
0000010: 10 00 00 00 01 00 02 00 44 ac 00 00 10 b1 02 00 ........D.......
0000020: 04 00 10 00 64 61 74 61 20 62 05 00 71 00 71 00 ....data b..q.q.
0000030: 6f 00 6f 00 79 00 79 00 75 00 75 00 63 00 63 00 o.o.y.y.u.u.c.c.
0000040: 3e 00 3e 00 1b 00 1b 00 07 00 07 00 fb ff fb ff >.>.............
0000050: 00 00 00 00 0c 00 0c 00 0f 00 0f 00 1c 00 1c 00 ................
0000060: 30 00 30 00 31 00 31 00 24 00 24 00 1e 00 1e 00 0.0.1.1.$.$.....
0000070: 24 00 24 00 31 00 31 00 2c 00 2c 00 28 00 28 00 $.$.1.1.,.,.(.(.
0000080: 31 00 31 00 3c 00 3c 00 36 00 36 00 31 00 31 00 1.1.<.<.6.6.1.1.
0000090: 39 00 39 00 40 00 40 00 3d 00 3d 00 30 00 30 00 9.9.@.@.=.=.0.0.
$ file arecord.wav
test.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 44100 Hz
$ file /tmp/filevXDDX6.wav
/tmp/filevXDDX6.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, stereo 44100 Hz
答案 0 :(得分：1)
您的程序没有将正确的样本数写入.wav文件。
snd_pcm_readi返回实际读取的帧数。
您只能将那么多帧写入输出。
duration * 1000 / sampleRate中的整数除法可能会四舍五入。
duration * 1000 / sampleRate * frames可能与您实际想要阅读的帧数不完全相同。
您应该重新构造循环以计算总帧数。