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ROM Usage With Respect to Various Synthesis Algorithms
6-14
6.4 ROM Usage With Respect to Various Synthesis Algorithms
The following table lists some possible synthesis options and their ROM
requirements. The models assume that just enough program space, as
necessary for storage of the synthesis algorithm, is used. The remainder of the
ROM is dedicated entirely to the speech data, with the goal of maximizing the
synthesis playback time.
If any two synthesis algorithms are to be used in combination, e.g., MELP and
LPC together, then a separate allocation must be made for each algorithm
within the same fixed pool of ROM. (The program space must hold two
algorithms, and the speech data is allocated in proportion to how much speech
duration is used for each algorithm.)
The bit-rates and program sizes given in this table are only approximations.
The estimates are applicable at the time of this printing, but they are subject
(and likely) to change. Also, the data-rate is sometimes dependent on the
properties of the speech.
← C614 Total ROM Storage →
32,768 words
BIST MELP program MELP speech data rate ≅ 2.4 k bits–per–second
2048 words 4.2 k words 26 k words ⇒ ∼ 170 seconds of speech
BIST
2048 words
CELP program
6 k words
CELP speech data rate ≅ 5.0 k bits-per-second
∼ 25 k words ⇒ ∼ 79 seconds of speech
BIST LPC program D6 LPC speech data rate ≅ 2.0 k bits-per-second
2048 words 1.5 k words 29 k words ⇒ ∼ 230 seconds of speech
BIST ADPCM program ADPCM speech data rate ≅ 32.0 k bits–per–second (@ 8 kHz S.R.)
2048 words 0.3 k words 30 k words ⇒ ∼ 15 seconds of speech
BIST 8–bit PCM speech data rate ≅ 64.0 k bits–per–second (@ 8 kHz S.R.)
2048 words 30 k words ⇒ ∼ 7.5 seconds of speech