ffmpeg之音频格式

 

样本格式

基于ffmpeg-4.3.2

相关头文件

#include <libavutil/samplefmt.h>

相关定义

音频样本格式:

enum AVSampleFormat {
    AV_SAMPLE_FMT_NONE = -1,
    AV_SAMPLE_FMT_U8,          ///< unsigned 8 bits
    AV_SAMPLE_FMT_S16,         ///< signed 16 bits
    AV_SAMPLE_FMT_S32,         ///< signed 32 bits
    AV_SAMPLE_FMT_FLT,         ///< float
    AV_SAMPLE_FMT_DBL,         ///< double

    AV_SAMPLE_FMT_U8P,         ///< unsigned 8 bits, planar
    AV_SAMPLE_FMT_S16P,        ///< signed 16 bits, planar
    AV_SAMPLE_FMT_S32P,        ///< signed 32 bits, planar
    AV_SAMPLE_FMT_FLTP,        ///< float, planar
    AV_SAMPLE_FMT_DBLP,        ///< double, planar
    AV_SAMPLE_FMT_S64,         ///< signed 64 bits
    AV_SAMPLE_FMT_S64P,        ///< signed 64 bits, planar

    AV_SAMPLE_FMT_NB           ///< Number of sample formats. DO NOT USE if linking dynamically
};

相关API

返回格式名称根据格式值

/**
 * Return the name of sample_fmt, or NULL if sample_fmt is not
 * recognized.
 */
const char *av_get_sample_fmt_name(enum AVSampleFormat sample_fmt);

返回样本格式值根据名称

/**
 * Return a sample format corresponding to name, or AV_SAMPLE_FMT_NONE
 * on error.
 */
enum AVSampleFormat av_get_sample_fmt(const char *name);

样本组合格式转换,planar/packed

/**
 * Return the planar<->packed alternative form of the given sample format, or
 * AV_SAMPLE_FMT_NONE on error. If the passed sample_fmt is already in the
 * requested planar/packed format, the format returned is the same as the
 * input.
 */
enum AVSampleFormat av_get_alt_sample_fmt(enum AVSampleFormat sample_fmt, int planar);

获取packed组合格式

/**
 * Get the packed alternative form of the given sample format.
 *
 * If the passed sample_fmt is already in packed format, the format returned is
 * the same as the input.
 *
 * @return  the packed alternative form of the given sample format or
            AV_SAMPLE_FMT_NONE on error.
 */
enum AVSampleFormat av_get_packed_sample_fmt(enum AVSampleFormat sample_fmt);

获取planar组合格式

/**
 * Get the planar alternative form of the given sample format.
 *
 * If the passed sample_fmt is already in planar format, the format returned is
 * the same as the input.
 *
 * @return  the planar alternative form of the given sample format or
            AV_SAMPLE_FMT_NONE on error.
 */
enum AVSampleFormat av_get_planar_sample_fmt(enum AVSampleFormat sample_fmt);

填充样本格式名称

/**
 * Generate a string corresponding to the sample format with
 * sample_fmt, or a header if sample_fmt is negative.
 *
 * @param buf the buffer where to write the string
 * @param buf_size the size of buf
 * @param sample_fmt the number of the sample format to print the
 * corresponding info string, or a negative value to print the
 * corresponding header.
 * @return the pointer to the filled buffer or NULL if sample_fmt is
 * unknown or in case of other errors
 */
char *av_get_sample_fmt_string(char *buf, int buf_size, enum AVSampleFormat sample_fmt);

返回每个样本的字节数

/**
 * Return number of bytes per sample.
 *
 * @param sample_fmt the sample format
 * @return number of bytes per sample or zero if unknown for the given
 * sample format
 */
int av_get_bytes_per_sample(enum AVSampleFormat sample_fmt);

检查样本组合格式是否为planar

/**
 * Check if the sample format is planar.
 *
 * @param sample_fmt the sample format to inspect
 * @return 1 if the sample format is planar, 0 if it is interleaved
 */
int av_sample_fmt_is_planar(enum AVSampleFormat sample_fmt);

获取给定音频参数所需的缓冲区大小

/**
 * Get the required buffer size for the given audio parameters.
 *
 * @param[out] linesize calculated linesize, may be NULL
 * @param nb_channels   the number of channels
 * @param nb_samples    the number of samples in a single channel
 * @param sample_fmt    the sample format
 * @param align         buffer size alignment (0 = default, 1 = no alignment)
 * @return              required buffer size, or negative error code on failure
 */
int av_samples_get_buffer_size(int *linesize, int nb_channels, int nb_samples,
                               enum AVSampleFormat sample_fmt, int align);

填充数据

/**
 * Fill plane data pointers and linesize for samples with sample
 * format sample_fmt.
 *
 * The audio_data array is filled with the pointers to the samples data planes:
 * for planar, set the start point of each channel's data within the buffer,
 * for packed, set the start point of the entire buffer only.
 *
 * The value pointed to by linesize is set to the aligned size of each
 * channel's data buffer for planar layout, or to the aligned size of the
 * buffer for all channels for packed layout.
 *
 * The buffer in buf must be big enough to contain all the samples
 * (use av_samples_get_buffer_size() to compute its minimum size),
 * otherwise the audio_data pointers will point to invalid data.
 *
 * @see enum AVSampleFormat
 * The documentation for AVSampleFormat describes the data layout.
 *
 * @param[out] audio_data  array to be filled with the pointer for each channel
 * @param[out] linesize    calculated linesize, may be NULL
 * @param buf              the pointer to a buffer containing the samples
 * @param nb_channels      the number of channels
 * @param nb_samples       the number of samples in a single channel
 * @param sample_fmt       the sample format
 * @param align            buffer size alignment (0 = default, 1 = no alignment)
 * @return                 >=0 on success or a negative error code on failure
 * @todo return minimum size in bytes required for the buffer in case
 * of success at the next bump
 */
int av_samples_fill_arrays(uint8_t **audio_data, int *linesize,
                           const uint8_t *buf,
                           int nb_channels, int nb_samples,
                           enum AVSampleFormat sample_fmt, int align);

分配一个样本缓冲区,并补充指针和大小

/**
 * Allocate a samples buffer for nb_samples samples, and fill data pointers and
 * linesize accordingly.
 * The allocated samples buffer can be freed by using av_freep(&audio_data[0])
 * Allocated data will be initialized to silence.
 *
 * @see enum AVSampleFormat
 * The documentation for AVSampleFormat describes the data layout.
 *
 * @param[out] audio_data  array to be filled with the pointer for each channel
 * @param[out] linesize    aligned size for audio buffer(s), may be NULL
 * @param nb_channels      number of audio channels
 * @param nb_samples       number of samples per channel
 * @param align            buffer size alignment (0 = default, 1 = no alignment)
 * @return                 >=0 on success or a negative error code on failure
 * @todo return the size of the allocated buffer in case of success at the next bump
 * @see av_samples_fill_arrays()
 * @see av_samples_alloc_array_and_samples()
 */
int av_samples_alloc(uint8_t **audio_data, int *linesize, int nb_channels,
                     int nb_samples, enum AVSampleFormat sample_fmt, int align);

分配一个样本缓冲区和指针,并填充大小

/**
 * Allocate a data pointers array, samples buffer for nb_samples
 * samples, and fill data pointers and linesize accordingly.
 *
 * This is the same as av_samples_alloc(), but also allocates the data
 * pointers array.
 *
 * @see av_samples_alloc()
 */
int av_samples_alloc_array_and_samples(uint8_t ***audio_data, int *linesize, int nb_channels,
                                       int nb_samples, enum AVSampleFormat sample_fmt, int align);

复制样本数据

测试失败

/**
 * Copy samples from src to dst.
 *
 * @param dst destination array of pointers to data planes
 * @param src source array of pointers to data planes
 * @param dst_offset offset in samples at which the data will be written to dst
 * @param src_offset offset in samples at which the data will be read from src
 * @param nb_samples number of samples to be copied
 * @param nb_channels number of audio channels
 * @param sample_fmt audio sample format
 */
int av_samples_copy(uint8_t **dst, uint8_t * const *src, int dst_offset,
                    int src_offset, int nb_samples, int nb_channels,
                    enum AVSampleFormat sample_fmt);

填充静音数据到缓冲区

/**
 * Fill an audio buffer with silence.
 *
 * @param audio_data  array of pointers to data planes
 * @param offset      offset in samples at which to start filling
 * @param nb_samples  number of samples to fill
 * @param nb_channels number of audio channels
 * @param sample_fmt  audio sample format
 */
int av_samples_set_silence(uint8_t **audio_data, int offset, int nb_samples,
                           int nb_channels, enum AVSampleFormat sample_fmt);