Hi Mark, ALSA SoC ML
In my understanding, "frame size" means "channel x physical width". linux/sound/core/pcm_native.c :: snd_pcm_hw_params() is doing so
static int snd_pcm_hw_params(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params) { ... => bits = snd_pcm_format_physical_width(runtime->format); runtime->sample_bits = bits; => bits *= runtime->channels; runtime->frame_bits = bits; ... }
But, soc-utils::snd_soc_params_to_frame_size() is using snd_pcm_format_width() instead of snd_pcm_format_physical_width(), In "2ch x 24bit data with 32bit width" case, above "frame_bits" will be "64", but, below "frame size" will be "48", I think. Am I wrong ?
int snd_soc_params_to_frame_size(struct snd_pcm_hw_params *params) { int sample_size;
=> sample_size = snd_pcm_format_width(params_format(params)); if (sample_size < 0) return sample_size;
=> return snd_soc_calc_frame_size(sample_size, params_channels(params), 1); }
About "TDM slot", in my understanding it is TDM channel number. TDM6 = 6ch = 6 slot, TDM8 = 8ch = 8 slot. Am I wrong ?? I'm asking because soc-utils :: snd_soc_calc_bclk() / snd_soc_calc_frame_size() have both "channles" and "slot" parameter. What is this "tdm_slots" means ?
int snd_soc_calc_frame_size(int sample_size, int channels, int tdm_slots) int snd_soc_calc_bclk(int fs, int sample_size, int channels, int tdm_slots)
Best regards --- Kuninori Morimoto