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dbry / adpcm-xq

Xtreme Quality IMA-ADPCM Encoder / Decoder
BSD 3-Clause "New" or "Revised" License
214 stars 46 forks source link

lost samples #1

Closed vostrenkov closed 8 years ago

vostrenkov commented 8 years ago

Hello! I have a question about your library: If i use adpcm_decode_block(...) function for data encoded by adpcm_encode_block(...) function, i have decoded data buffer a 7 samples shotrer then input buffer for encoding (the block size doesnt matter). I'm not good at acoustic science, but i think it is not right, isn't it?

dbry commented 8 years ago

I think the most likely reason is that you must call adpcm_encode_block() with a inbufcount equal to one greater than a multiple of 8. If you use a multiple of 8, you will lose exactly 7 samples. You can read about this at the very top of the adpcm-lib.c file.

I hope this fixes your problem.

-David

dbry commented 8 years ago

Oops...I didn't mean to close the issue. Please comment if you still have trouble.

vostrenkov commented 8 years ago

Thank you for response! Yes, i tried inbuf equal to one greater than a multiple of 8 and i heard scratches in output sound. If i lose 7 samples there are much less scratches. Probably, this is my fault. Anyway, this library provides the best quality of sound of all ADPCM codecs i have tried, so thank you very much for your help!

dbry commented 8 years ago

There should not be any transient sounds. You should be able to make sure the encoder/decoder is working correctly by using the command-line tester. Please feel free to let me know if you continue to have trouble, and I can perhaps look over your code.

vostrenkov commented 8 years ago

I beleive encoder/decoder work fine in your application. I think my problem is the way of receiving incoming PCM data - it comes from PDM data and some filtering and decimation. In this case input data are always is buffer equal a multiple of 8 and it corrupts if i try to get one more sample. I think this issue could be closed, thanks for your help!

dbry commented 8 years ago

Ah, okay. You'll have to create your own buffer then and keep track of the extra samples. Obviously just throwing away samples will not sound good. Good luck!