backw_ctx = swr_alloc_set_opts(backw_ctx, in_ch_layout, in_sample_fmt, in_sample_rate,
out_ch_layout, out_sample_fmt, out_sample_rate,
0, 0);
backw_ctx = swr_alloc_set_opts(backw_ctx, in_ch_layout, in_sample_fmt, in_sample_rate,
out_ch_layout, out_sample_fmt, out_sample_rate,
0, 0);