diff options
| author | Martijn van Beurden <mvanb1@gmail.com> | 2014-08-10 10:59:29 +0200 |
|---|---|---|
| committer | Erik de Castro Lopo <erikd@mega-nerd.com> | 2014-09-22 18:03:24 +1000 |
| commit | 29a28338c3c0aaba2e5b074a6e757a6cc3f0959e (patch) | |
| tree | 3188a4bcde8ccf7789cc8fb35fb9fcd31ed3195f /man | |
| parent | ffa55423e0cc159b9a84cbde9e59e37921879475 (diff) | |
| download | flac-29a28338c3c0aaba2e5b074a6e757a6cc3f0959e.tar.gz | |
Add partial_tukey and punchout_tukey apodization functions
Adds two new apodization functions that seem to perform better than
the apodization functions currently in the codebase and fixes three
existing windows as well.
Its important to note that this patch only affects the encoder stage
that evaluates various possible predictors. Audio encoded with these
new windows will still decode with existing legacy decoders.
= Theory =
These functions are used to window the audio data at the predictor
stage. These news functions enable the use of only part of the signal
to generate a predictor. This helps because short transients can
introduce noise into the predictor. The predictor becomes very good
at prediciting one part of the signal, instead of mediocre for the
whole block.
Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>
Diffstat (limited to 'man')
| -rw-r--r-- | man/flac.1 | 6 | ||||
| -rw-r--r-- | man/flac.sgml | 4 |
2 files changed, 8 insertions, 2 deletions
@@ -280,12 +280,16 @@ Highest compression. Currently synonymous with -8. Do exhaustive model search (expensive!) .TP \fB-A \fIfunction\fB, --apodization=\fIfunction\fB\fR -Window audio data with given the apodization function. The functions are: bartlett, bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop, gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle, triangle, tukey(P), welch. +Window audio data with given the apodization function. The functions are: bartlett, bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop, gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle, triangle, tukey(P), partial_tukey(n[/ov[/P]]), punchout_tukey(n[/ov[/P]]), welch. For gauss(STDDEV), STDDEV is the standard deviation (0<STDDEV<=0.5). For tukey(P), P specifies the fraction of the window that is tapered (0<=P<=1; P=0 corresponds to "rectangle" and P=1 corresponds to "hann"). +For partial_tukey(n) and punchout_tukey(n), n apodization functions are added that span different parts of each block. Values of 2 to 6 seem to yield sane results. If necessary, an overlap can be specified, as can be the taper parameter, for example partial_tukey(2/0.2) or partial_tukey(2/0.2/0.5). ov should be smaller than 1 and can be negative. + +Please note that P, STDDEV and ov are locale specific, so a comma as decimal separator might be required instead of a dot. + More than one -A option (up to 32) may be used. Any function that is specified erroneously is silently dropped. The encoder chooses suitable defaults in the absence of any -A options; any -A option specified replaces the default(s). When more than one function is specified, then for every subframe the encoder will try each of them separately and choose the window that results in the smallest compressed subframe. Multiple functions can greatly increase the encoding time. diff --git a/man/flac.sgml b/man/flac.sgml index 7fa410b5..37525ce5 100644 --- a/man/flac.sgml +++ b/man/flac.sgml @@ -612,9 +612,11 @@ <term><option>-A</option> <replaceable>function</replaceable>, <option>--apodization</option>=<replaceable>function</replaceable></term> <listitem> - <para>Window audio data with given the apodization function. The functions are: bartlett, bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop, gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle, triangle, tukey(P), welch.</para> + <para>Window audio data with given the apodization function. The functions are: bartlett, bartlett_hann, blackman, blackman_harris_4term_92db, connes, flattop, gauss(STDDEV), hamming, hann, kaiser_bessel, nuttall, rectangle, triangle, tukey(P), partial_tukey(n[/ov[/P]]), punchout_tukey(n[/ov[/P]]), welch.</para> <para>For gauss(STDDEV), STDDEV is the standard deviation (0<STDDEV<=0.5).</para> <para>For tukey(P), P specifies the fraction of the window that is tapered (0<=P<=1; P=0 corresponds to "rectangle" and P=1 corresponds to "hann").</para> + <para>For partial_tukey(n) and punchout_tukey(n), n apodization functions are added that span different parts of each block. Values of 2 to 6 seem to yield sane results. If necessary, an overlap can be specified, as can be the taper parameter, for example partial_tukey(2/0.2) or partial_tukey(2/0.2/0.5). ov should be smaller than 1 and can be negative.</para> + <para>Please note that P, STDDEV and ov are locale specific, so a comma as decimal separator might be required instead of a dot.</para> <para>More than one -A option (up to 32) may be used. Any function that is specified erroneously is silently dropped. The encoder chooses suitable defaults in the absence of any -A options; any -A option specified replaces the default(s).</para> <para>When more than one function is specified, then for every subframe the encoder will try each of them separately and choose the window that results in the smallest compressed subframe. Multiple functions can greatly increase the encoding time.</para> </listitem> |