Allocate SwrContext if needed and set/reset common parameters.
This function does not require s to be allocated with swr_alloc(). On the
other hand, swr_alloc() can use swr_alloc_set_opts() to set the parameters
on the allocated context.
@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)
@param in_ch_layout input channel layout (AV_CH_LAYOUT_*)
@param in_sample_fmt input sample format (AV_SAMPLE_FMT_*).
@param in_sample_rate input sample rate (frequency in Hz)
@param log_offset logging level offset
@param log_ctx parent logging context, can be NULL
@see swr_init(), swr_free()
@return NULL on error, allocated context otherwise
Allocate SwrContext if needed and set/reset common parameters.
This function does not require s to be allocated with swr_alloc(). On the other hand, swr_alloc() can use swr_alloc_set_opts() to set the parameters on the allocated context.
@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) @param in_ch_layout input channel layout (AV_CH_LAYOUT_*) @param in_sample_fmt input sample format (AV_SAMPLE_FMT_*). @param in_sample_rate input sample rate (frequency in Hz) @param log_offset logging level offset @param log_ctx parent logging context, can be NULL
@see swr_init(), swr_free() @return NULL on error, allocated context otherwise