diff --git a/libswresample/swresample.h b/libswresample/swresample.h index 838fb5cd35..e4bbebae16 100644 --- a/libswresample/swresample.h +++ b/libswresample/swresample.h @@ -189,6 +189,7 @@ typedef struct SwrContext SwrContext; * AV_OPT_SEARCH_FAKE_OBJ for examining options. * * @see av_opt_find(). + * @return the AVClass of SwrContext */ const AVClass *swr_get_class(void); @@ -211,6 +212,7 @@ struct SwrContext *swr_alloc(void); /** * Initialize context after user parameters have been set. * + * @param[in,out] s Swr context to initialize * @return AVERROR error code in case of failure. */ int swr_init(struct SwrContext *s); @@ -218,6 +220,8 @@ int swr_init(struct SwrContext *s); /** * Check whether an swr context has been initialized or not. * + * @param[in] s Swr context to check + * @see swr_init() * @return positive if it has been initialized, 0 if not initialized */ int swr_is_initialized(struct SwrContext *s); @@ -229,7 +233,7 @@ int swr_is_initialized(struct SwrContext *s); * other hand, swr_alloc() can use swr_alloc_set_opts() to set the parameters * on the allocated context. * - * @param s Swr context, can be NULL + * @param s existing Swr context if available, or NULL if not * @param out_ch_layout output channel layout (AV_CH_LAYOUT_*) * @param out_sample_fmt output sample format (AV_SAMPLE_FMT_*). * @param out_sample_rate output sample rate (frequency in Hz) @@ -256,6 +260,8 @@ struct SwrContext *swr_alloc_set_opts(struct SwrContext *s, /** * Free the given SwrContext and set the pointer to NULL. + * + * @param[in] s a pointer to a pointer to Swr context */ void swr_free(struct SwrContext **s); @@ -266,6 +272,8 @@ void swr_free(struct SwrContext **s); * swr_init() can also be used without swr_close(). * This function is mainly provided for simplifying the usecase * where one tries to support libavresample and libswresample. + * + * @param[in,out] s Swr context to be closed */ void swr_close(struct SwrContext *s); @@ -301,12 +309,16 @@ int swr_convert(struct SwrContext *s, uint8_t **out, int out_count, * timestamps are in 1/(in_sample_rate * out_sample_rate) units. * * @note There are 2 slightly differently behaving modes. - * First is when automatic timestamp compensation is not used, (min_compensation >= FLT_MAX) + * @li When automatic timestamp compensation is not used, (min_compensation >= FLT_MAX) * in this case timestamps will be passed through with delays compensated - * Second is when automatic timestamp compensation is used, (min_compensation < FLT_MAX) - * in this case the output timestamps will match output sample numbers + * @li When automatic timestamp compensation is used, (min_compensation < FLT_MAX) + * in this case the output timestamps will match output sample numbers. + * See ffmpeg-resampler(1) for the two modes of compensation. * - * @param pts timestamp for the next input sample, INT64_MIN if unknown + * @param s[in] initialized Swr context + * @param pts[in] timestamp for the next input sample, INT64_MIN if unknown + * @see swr_set_compensation(), swr_drop_output(), and swr_inject_silence() are + * function used internally for timestamp compensation. * @return the output timestamp for the next output sample */ int64_t swr_next_pts(struct SwrContext *s, int64_t pts); @@ -321,17 +333,30 @@ int64_t swr_next_pts(struct SwrContext *s, int64_t pts); */ /** - * Activate resampling compensation. + * Activate resampling compensation ("soft" compensation). This function is + * internally called when needed in swr_next_pts(). + * + * @param[in,out] s allocated Swr context. If it is not initialized, + * or SWR_FLAG_RESAMPLE is not set, swr_init() is + * called with the flag set. + * @param[in] sample_delta delta in PTS per sample + * @param[in] compensation_distance number of samples to compensate for + * @return >= 0 on success, AVERROR error codes if: + * @li @c s is NULL, + * @li @c compensation_distance is less than 0, + * @li @c compensation_distance is 0 but sample_delta is not, + * @li compensation unsupported by resampler, or + * @li swr_init() fails when called. */ int swr_set_compensation(struct SwrContext *s, int sample_delta, int compensation_distance); /** * Set a customized input channel mapping. * - * @param s allocated Swr context, not yet initialized - * @param channel_map customized input channel mapping (array of channel - * indexes, -1 for a muted channel) - * @return AVERROR error code in case of failure. + * @param[in,out] s allocated Swr context, not yet initialized + * @param[in] channel_map customized input channel mapping (array of channel + * indexes, -1 for a muted channel) + * @return >= 0 on success, or AVERROR error code in case of failure. */ int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map); @@ -342,7 +367,7 @@ int swr_set_channel_mapping(struct SwrContext *s, const int *channel_map); * @param matrix remix coefficients; matrix[i + stride * o] is * the weight of input channel i in output channel o * @param stride offset between lines of the matrix - * @return AVERROR error code in case of failure. + * @return >= 0 on success, or AVERROR error code in case of failure. */ int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride); @@ -355,11 +380,27 @@ int swr_set_matrix(struct SwrContext *s, const double *matrix, int stride); /** * Drops the specified number of output samples. + * + * This function, along with swr_inject_silence(), is called by swr_next_pts() + * if needed for "hard" compensation. + * + * @param s allocated Swr context + * @param count number of samples to be dropped + * + * @return >= 0 on success, or a negative AVERROR code on failure */ int swr_drop_output(struct SwrContext *s, int count); /** * Injects the specified number of silence samples. + * + * This function, along with swr_drop_output(), is called by swr_next_pts() + * if needed for "hard" compensation. + * + * @param s allocated Swr context + * @param count number of samples to be dropped + * + * @return >= 0 on success, or a negative AVERROR code on failure */ int swr_inject_silence(struct SwrContext *s, int count); @@ -375,13 +416,17 @@ int swr_inject_silence(struct SwrContext *s, int count); * for upsampling and the input sample rate. * * @param s swr context - * @param base timebase in which the returned delay will be - * if its set to 1 the returned delay is in seconds - * if its set to 1000 the returned delay is in milli seconds - * if its set to the input sample rate then the returned delay is in input samples - * if its set to the output sample rate then the returned delay is in output samples - * an exact rounding free delay can be found by using LCM(in_sample_rate, out_sample_rate) - * @returns the delay in 1/base units. + * @param base timebase in which the returned delay will be: + * @li if it's set to 1 the returned delay is in seconds + * @li if it's set to 1000 the returned delay is in milliseconds + * @li if it's set to the input sample rate then the returned + * delay is in input samples + * @li if it's set to the output sample rate then the returned + * delay is in output samples + * @li if it's the least common multiple of in_sample_rate and + * out_sample_rate then an exact rounding-free delay will be + * returned + * @returns the delay in 1 / @c base units. */ int64_t swr_get_delay(struct SwrContext *s, int64_t base);