I have files, which I recorded back in 90s with ESS ES688 AudioDrive card, 4-bit voice optimized codec. Nowadays I do not possess the card any more and proprietary codec is no longer supported or I can't find any hints how to decode it. Here ffmpeg output:
[wav @ 0x55cc15d2c900] Estimating duration from bitrate, this may be inaccurate [wav @ 0x55cc15d2c900] Could not find codec parameters for stream 0 (Audio: none ( / 0xE688), 8000 Hz, 1 channels, 33 kb/s): unknown codec Consider increasing the value for the 'analyzeduration' and 'probesize' options Guessed Channel Layout for Input Stream #0.0 : mono Input #0, wav, from 'MY.WAV': Duration: 00:04:48.64, bitrate: 33 kb/s Stream #0:0: Audio: none ( / 0xE688), 8000 Hz, mono, 33 kb/s
Is there any way to do it without actual physical card and compatible PC hardware? Can sound card emulator solve this?
I have not found any hints of how 4-bit per sample ended in the WAV file, but eg this ES688 AudioDrive chip's datasheet mentions programmable sample rate from 4000 to 44100 Hz so my assumption is: When I requested low bit-rate I ended up with having a non-standard WAV-file with two samples per byte...