基于ALSA lib录音接口

接口文件 record_interface.h

/** * @file record_interface.h * @brief For the operation of record API */#ifndef __record_INTERFACE_HEAD__#define __record_INTERFACE_HEAD__#include <stdio.h>#include <malloc.h>#include <unistd.h>#include <stdlib.h>#include <string.h>#include <getopt.h>#include <fcntl.h>#include <ctype.h>#include <errno.h>#include <limits.h>#include <time.h>#include <locale.h>#include <sys/unistd.h>#include <sys/stat.h>#include <sys/types.h>#include "alsa/asoundlib.h"#include <assert.h>typedef unsigned char  uint8_t;typedef unsigned short uint16_t;typedef unsigned int   uint32_t;typedef struct {    /**     * @brief Alsa handle.     */    snd_pcm_t *handle;    /**     * @brief Alsa log Output redirection.     */    snd_output_t *log;    /**     * @brief Alsa internal audio cache buffer size.     */    snd_pcm_uframes_t buffer_size;    /**     * @brief Data format.     */    snd_pcm_format_t format;    /**     * @brief The number of channels.     */    uint16_t channels;    /**     * @brief The number of bit per sample point.     */    size_t bits_per_sample;    /**     * @brief The number of bit per frame.     */    size_t bits_per_frame;    /**     * @brief The amount of frame required to record.     */    snd_pcm_uframes_t chunk_size;    /**     * @brief The number of bytes required to be recorded is matched with the     * chunk_size.     */    size_t chunk_bytes;    /**     * @brief Point to the recording data buffer, the size is chunk_bytes bytes,     * have chunk_size frame.     */    uint8_t *data_buf;} record_handle_t;typedef struct {    /*     * Specifies data format.     * SND_PCM_FORMAT_S16_LE;     * SND_PCM_FORMAT_S8;     * SND_PCM_FORMAT_UNKNOWN;     * All references at sound/asound.h     */    snd_pcm_format_t format;    /**     * @brief Specifies the number of channels.     */    uint16_t channels;    /**     * @brief frequence of sample     */    uint32_t sample_rate;} record_params_t;/** * @brief Get the handle for the recording. * * @param record_params Recording parameters. * * @return Record handle on success otherwise NULL is returned. */record_handle_t *mozart_get_record_handle(record_params_t record_params);/** * @brief Get the recording data, the size is chunk_bytes bytes. * * @param record_handle * * @return Return a pointer to data on success otherwise NULL is returned. */uint8_t *mozart_record_get_data(record_handle_t * record_handle);/** * @brief Release record handle after call mozart_get_record_handle. * * @param record_handle */void mozart_release_record_handle(record_handle_t * record_handle);#endif /* __record_INTERFACE_HEAD__ */

实现文件 record.c

/** * @file record.c * @brief For the operation of record API */#include "record_interface.h"#define DEBUG(x,y...)   {printf("[ %s : %s : %d] ",__FILE__, __func__, __LINE__); printf(x,##y); printf("\n");}#define ERROR(x,y...)   {printf("[ %s : %s : %d] ",__FILE__, __func__, __LINE__); printf(x,##y); printf("\n");}static int record_set_params(record_handle_t * record_handle, record_params_t record_params){    snd_pcm_hw_params_t *hwparams;    uint32_t exact_rate;    uint32_t buffer_time, period_time;    /* Allocate the snd_pcm_hw_params_t structure on the stack. */    snd_pcm_hw_params_alloca(&hwparams);    /* Init hwparams with full configuration space */    if (snd_pcm_hw_params_any(record_handle->handle, hwparams) < 0) {        ERROR("Error snd_pcm_hw_params_any");        goto ERR_SET_PARAMS;    }    if (snd_pcm_hw_params_set_access(record_handle->handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED) < 0) {        ERROR("Error snd_pcm_hw_params_set_access");        goto ERR_SET_PARAMS;    }    if (snd_pcm_hw_params_set_format(record_handle->handle, hwparams, record_params.format) < 0) {        ERROR("Error snd_pcm_hw_params_set_format");        goto ERR_SET_PARAMS;    }    record_handle->format = record_params.format;    /* Set number of channels */    if (snd_pcm_hw_params_set_channels(record_handle->handle, hwparams, record_params.channels) < 0) {        ERROR("Error snd_pcm_hw_params_set_channels");        goto ERR_SET_PARAMS;    }    record_handle->channels = record_params.channels;    /* Set sample rate. If the exact rate is not supported */    /* by the hardware, use nearest possible rate.       */    exact_rate = record_params.sample_rate;    if (snd_pcm_hw_params_set_rate_near(record_handle->handle, hwparams, &exact_rate, 0) < 0) {        ERROR("Error snd_pcm_hw_params_set_rate_near");        goto ERR_SET_PARAMS;    }    if (record_params.sample_rate != exact_rate) {        ERROR("The rate %d Hz is not supported by your hardware. ==> Using %d Hz instead.",            record_params.sample_rate, exact_rate);    }    if (snd_pcm_hw_params_get_buffer_time_max(hwparams, &buffer_time, 0) < 0) {        ERROR("Error snd_pcm_hw_params_get_buffer_time_max");        goto ERR_SET_PARAMS;    }    if (buffer_time > 500000) buffer_time = 500000;    period_time = buffer_time / 4;    if (snd_pcm_hw_params_set_buffer_time_near(record_handle->handle, hwparams, &buffer_time, 0) < 0) {        ERROR("Error snd_pcm_hw_params_set_buffer_time_near");        goto ERR_SET_PARAMS;    }    if (snd_pcm_hw_params_set_period_time_near(record_handle->handle, hwparams, &period_time, 0) < 0) {        ERROR("Error snd_pcm_hw_params_set_period_time_near");        goto ERR_SET_PARAMS;    }    /* Set hw params */    if (snd_pcm_hw_params(record_handle->handle, hwparams) < 0) {        ERROR("Error snd_pcm_hw_params(handle, params)");        goto ERR_SET_PARAMS;    }    snd_pcm_hw_params_get_period_size(hwparams, &record_handle->chunk_size, 0);    snd_pcm_hw_params_get_buffer_size(hwparams, &record_handle->buffer_size);    if (record_handle->chunk_size == record_handle->buffer_size) {        ERROR(("Can't use period equal to buffer size (%lu == %lu)"), record_handle->chunk_size, record_handle->buffer_size);        goto ERR_SET_PARAMS;    }    //通过fomart获取每sample的bit数    record_handle->bits_per_sample = snd_pcm_format_physical_width(record_params.format);    //把frame定义为一个sample的数据，包括每个channel    record_handle->bits_per_frame = record_handle->bits_per_sample * record_params.channels;    //计算录chunk_size个frame需要的byte数    record_handle->chunk_bytes = record_handle->chunk_size * record_handle->bits_per_frame / 8;    //开辟录音buffer    record_handle->data_buf = (uint8_t *)malloc(record_handle->chunk_bytes);    if (!record_handle->data_buf) {        ERROR("Error malloc: [data_buf]");        goto ERR_SET_PARAMS;    }    return 0;ERR_SET_PARAMS:    return -1;}record_handle_t *mozart_get_record_handle(record_params_t record_params){    char *devicename = "default";    record_handle_t *record_handle;    record_handle = (record_handle_t *)malloc(sizeof(record_handle_t));    memset(record_handle, 0x0, sizeof(record_handle_t));    if (snd_output_stdio_attach(&record_handle->log, stderr, 0) < 0) {        ERROR("Error snd_output_stdio_attach");        free(record_handle);        return NULL;    }    if (snd_pcm_open(&(record_handle->handle), devicename, SND_PCM_STREAM_CAPTURE, 0) < 0) {        ERROR("Error snd_pcm_open [ %s]", devicename);        free(record_handle);        return NULL;    }    if (record_set_params(record_handle, record_params) < 0) {        ERROR("Error set_snd_pcm_params");        free(record_handle);        return NULL;    }    //snd_pcm_dump(record_handle->handle, record_handle->log);    return record_handle;}static ssize_t read_pcm(record_handle_t *record_handle){    ssize_t r;    size_t result = 0;    size_t count = record_handle->chunk_size;    uint8_t *data = record_handle->data_buf;    while (count > 0) {        //录count个frame到data中        r = snd_pcm_readi(record_handle->handle, data, count);        if (r == -EAGAIN || (r >= 0 && (size_t)r < count)) {            snd_pcm_wait(record_handle->handle, 1000);        } else if (r == -EPIPE) {            snd_pcm_prepare(record_handle->handle);            fprintf(stderr, "<<<<<<<<<<<<<<< Buffer Underrun >>>>>>>>>>>>>>>\n");        } else if (r == -ESTRPIPE) {            fprintf(stderr, "<<<<<<<<<<<<<<< Need suspend >>>>>>>>>>>>>>>\n");        } else if (r < 0) {            fprintf(stderr, "Error snd_pcm_readi: [%s]", snd_strerror(r));            return -1;        }        if (r > 0) {            result += r;            count -= r;            data += r * record_handle->bits_per_frame / 8;        }    }    return result;}uint8_t *mozart_record_get_data(record_handle_t * record_handle){    if (read_pcm(record_handle) != record_handle->chunk_size)        return NULL;    return record_handle->data_buf;}void mozart_release_record_handle(record_handle_t * record_handle){    snd_pcm_drain(record_handle->handle);    free(record_handle->data_buf);    snd_output_close(record_handle->log);    snd_pcm_close(record_handle->handle);}