DSP Group Truespeech: Difference between revisions
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* Format tag: 0x22 | * Format tag: 0x22 | ||
* Company: [[DSP Group]] | * Company: [[DSP Group]] | ||
This is the codec developed by [[DSP Group]]. It operates on 8000 Hz, 16-bit mono [[PCM]] and have some fixed bitrates, Windows version supports 15:1 compression (~1 Kbps) only. | |||
== Technical details (for standard scheme) == | |||
This codec employs LPC (Linear Predictive Coding) as almost every speech codec does. | |||
Frame (240 samples) is divided into 4 subframes. | |||
Packed frame data holds 8-order filter used in synthesis, 4x7 pulse positions and values, offset in previously decoded frame. | |||
Decoding flow: | |||
unpack frame data | |||
reconstruct packed filter | |||
merge this filter with previous to create 4 filters for each subframe | |||
for each subframe { | |||
apply twopoint filter on some saved data | |||
place pulses (7 pulses for each subframe max) | |||
update saved filter | |||
apply main filter to subframe data (mostly pulses) | |||
} | |||
[[Category: Audio Codecs]] | [[Category: Audio Codecs]] |
Revision as of 22:55, 8 February 2006
- Format tag: 0x22
- Company: DSP Group
This is the codec developed by DSP Group. It operates on 8000 Hz, 16-bit mono PCM and have some fixed bitrates, Windows version supports 15:1 compression (~1 Kbps) only.
Technical details (for standard scheme)
This codec employs LPC (Linear Predictive Coding) as almost every speech codec does.
Frame (240 samples) is divided into 4 subframes.
Packed frame data holds 8-order filter used in synthesis, 4x7 pulse positions and values, offset in previously decoded frame.
Decoding flow:
unpack frame data reconstruct packed filter merge this filter with previous to create 4 filters for each subframe for each subframe { apply twopoint filter on some saved data place pulses (7 pulses for each subframe max) update saved filter apply main filter to subframe data (mostly pulses) }