Hello Srinivas,
On 08/01/2017 02:52 PM, Srinivas Kandagatla wrote:
As example, if you configure bus in Left justified format with 24 bits sample length, 32 bits application samples should be truncated to 24 bits samples at ADV7533 I2S interface level (LSB dropped).
May be we can do that to make the user happy but isn't this just truncate the resolution to 24Bit then?
And it's a false indication that we are supporting 32bit samples. Which am not very happy with.
This is what the sample_bits field in the DAI structure is for.ya.
But still reporting that driver supports 32 bit samples when it does not really support all 32 bits, is kinda misleading to user. Isn't it?
And the driver would be end up with hacked up code for each case.
By experience, this is usual. As example, if you have a look to codec ad193x (i take one randomly) it support 16, 20, 24 and 32 bits frames. But if you have a look to AD1939 data-sheet it supports 24-bits conversion. Some other examples could be 13-bits DAC/ADC with 16 bits samples.
In term of audio quality, truncation to a 24 bits sample should generate an negligible additional error equal to the LSB bit: -20log(2^24)= -144dB.
It is just a personal opinion, but if have the choice between do truncation in software (application or alsa-lib) and in hardware, i would prefer the second one.
Regards arnaud