Ubuntu Manpage: squishyball - perform sample comparison testing on the command line

Provided by: squishyball_0.1~svn18880-2_amd64

NAME

       squishyball - perform sample comparison testing on the command line

SYNOPSIS

       squishyball [options] fileA [fileB [fileN...]] [> results.txt]

DESCRIPTION

       squishyball  is  a  simple  command-line utility for performing double-blind A/B, A/B/X or
       X/X/Y testing on the command line.  The user specifies two input files to be compared  and
       uses  the  keyboard  during playback to flip between the randomized samples to perform on-
       the-fly comparisons.  After a predetermined number of trials, squishyball prints the trial
       results  to  stdout  and  exits.   Results  (stdout)  may  be redirected to a file without
       affecting interactive use of the terminal.

       squishyball can also be used to perform casual, non-randomized comparisons of groups of up
       to ten samples; this is the default mode of operation.

TEST TYPES

-a --ab
Perform A/B test on two input samples.

A/B testing randomizes the order of two input samples and presents them, unnamed,
as sample 'A' and sample 'B'. In each trial the user selects A or B as the
preferred sample. The samples are then re-randomized for the next trial. This
test is useful for establishing relative or preferred quality between two samples.

-b --abx
Perform A/B/X test on two input samples.

A/B/X presents two input samples, unrandomized, as sample 'A' and sample 'B'. A
third sample 'X' is chosen randomly from either 'A' or 'B'. In each trial, the
user selects A or B as the sample believed to be the same as X. X is then re-
randomized for the next trial. This test is useful for determining if any
differences are audible between two samples and to what confidence level.

Note that because the A and B samples are not randomized (they are presented in the
order given on the command line as per standard industry practice), an A/B/X test
does not eliminate ordering bias. A stronger version of this test that randomizes
all samples is the X/X/Y test below.

-c --casual
Perform casual comparison of up to ten samples (default).

Casual comparison mode does not randomize the input samples or perform multiple
trials. It simply provides a convenient way to rapidly flip back and forth within
a group of up to ten samples.

-x --xxy
Perform randomized X/X/Y test on two input samples.

X/X/Y testing is a form of A/B/X testing in which the order of all samples is
randomized and the position of the 'X' sample is not known ahead of time to be in
the third position. In each trial, the user selects which of sample 1, 2 or 3 is
believed to be the sample that is different from the other two. This test is useful
for determining if any differences are audible between two samples and to what
confidence level. It is a stronger version of the A/B/X test that eliminates
sample order bias.

OTHER OPTIONS

-B --beep-flip
Mark transitions between samples with a short beep.

-d --device N|device
If a number, output to Nth available sound device. If a device name, use output
device matching that device name. The backend audio driver is selected
automatically based on the device name provided.

-D --force-dither
Always use dither when down-converting to 16-bit samples for playback on audio
devices that do not support 24-bit playback. By default, uncompressed samples are
always dithered, but lossy formats (such as Vorbis) are simply rounded. See the
section CONVERSION AND DITHER below for more details.

-e --end-time [[hh:]mm:]ss[.ff]
Set sample end time for playback.

-g --gabbagabbahey | --score-display
Show running score and probability figures of trials so far while testing. Can only
be used with -a, -b, or -x.

-h --help
Print usage summary to stdout and exit.

-M --mark-flip
Mark transitions between samples with a short period of silence (default).

-n --trials n
Set desired number of comparison trials (default: 20).

-r --restart-after
Set 'restart-after mode', where sample playback restarts from start point after
every trial.

-R --restart-every
Set 'restart-every mode', where sample playback restarts from start point after
'flip' as well as after every trial.

-s --start-time [[hh:]mm:]ss[.ff]
Set start time within sample for playback

-S --seamless-flip
Do not mark transitions between samples; flip with a seamless crossfade.

-t --force-truncate
Always round/truncate (never dither) when down-converting samples to 16-bit for
playback on audio devices that do not support 24-bit output. See the section
CONVERSION AND DITHER below for more details.

-v --verbose
Produce more and more detailed progress information and warnings.

-V --version
Print version and exit.

KEYBOARD INTERACTION

       a, b, x
              Switch between A and B samples (A/B mode), or A, B and X samples (A/B/X mode).

       A, B   Select  A  or B as preferred sample (A/B mode), or sample A or sample B as match to
              sample X (A/B/X testing mode).

       1, 2, 3...
              Switch between first, second, third  [etc]  samples  (X/X/Y  testing  mode,  casual
              comparison mode).

       !, @, #
              Indicate the 'odd sample out' as sample 1, 2, or 3 (X/X/Y testing mode).

       <del>, <ins>
              Undo/redo previous trial result selection.

       <enter>
              Choose current sample for this trial.

       <-, -> Seek back/forward two seconds, +shift for ten seconds.

       <up/down>
              Select sample in sample list (casual mode).

       <space>
              Pause/resume playback.

       <backspace>
              Reset playback to start point.

       e      Set end playback point to current playback time (see also -e above).

       E      Reset end playback time to end of sample.

       f      Toggle through beep-flip/mark-flip/seamless-flip modes (see -B, -M, and -S above).

       r      Toggle through restart-after/restart-every/no-restart modes (see -r and -R above).

       s      Set start playback point to current playback time (see also -s above).

       S      Reset start playback time to beginning of sample.

       ?      Print this keymap.  The keymap will not be printed if the terminal has insufficient
              rows to do so.

       ^c     Abort testing early.

SUPPORTED FILE TYPES

       WAV/WAVEX
              8-, 16-, 24-bit linear integer PCM (format 1), 32-bit float (format 3)

       AIFF/AIFF-C
              8-, 16-, 24-bit linear integer PCM, 32-bit floating point

       FLAC/OggFLAC
              16- and 24-bit

       SW     Mono signed 16-bit little endian 48000Hz raw with a .sw extension

       OggVorbis
              all Vorbis I files

CONVERSION AND DITHER

squishyball loads all linear PCM file types at native bit depth. Uncompressed floating
point files (eg, 32 bit floating point WAV) are converted to 24-bit integer PCM. Ogg
Vorbis files are also decoded to 24-bit.

Files are 'reconciled' to identical channel ordering, length and bit-depth before playback
begins so that CPU and memory resources usage during playback should be identical for both
samples. When 24-bit playback is available and at least one sample is 24-bit, all samples
are promoted to 24 bits. If 24-bit playback is unavailable, 24-bit samples are demoted to
16 bits.

Floating point samples (32-bit) are not dithered when converting to 24-bit. 24-bit and
floating point (32 bit) samples are dithered using a TPDF when down-conversion to 16-bit
is necessary. Lossy-encoded samples (eg Ogg Vorbis files) are an exception; they are not
dithered by default during down-conversion. This behavior can be overridden by -D, which
forces dithering for lossy files as well. Down-conversion dithering can be disabled for
all input types with -t.

Samples are checked for clipping at load time. Floating point samples can be checked
accurately. Integer samples are checked heuristically; two or more consecutive full-range
samples in a channel are counted as clipped. If any definitely or probably clipped
samples are found, squishyball issues a warning.

IMPORTANT USAGE NOTES

Playback Depth and Rate

Many modern audio playback systems (such as PulseAudio or the ALSA 'default'
device) give no means of determining if the requested playback paramters are
actually being used by the hardware, or if the audio system is helpfully converting
everything to some other supported depth/rate. When using these systems,
squishyball has no way of knowing if 16-/24-bit playback or sample rate is being
honored. Automatic conversion will almost always negatively affect sample quality.

Flip-Mode Choice

Silent Mode smoothly transitions between samples. It allows the most direct
comparison between signals without any intervening auditory distraction. However,
the temporary combination of different signals may cause unintended cancellation
and comb-filtering effects that can give away the 'unknown' sample just as a 'pop'
from an instantaneous transition would.

Mark Mode quickly fades to silence before flipping to another sample, marking the
transition. Because the samples never overlap, crosslap artifacts cannot
contaminate trial results. However, the audible dip between samples may distract
from listening, potentially making it slightly more difficult to detect legitimate
artifacts.

Beep Mode is similar to mark mode but adds a soft 'beep' to mark where the
transition occurs. It makes the transition point especially obvious. It does not
crosslap the samples; one sample is faded completely before the second is mixed in
as in mark mode.

AUTHORS

       Monty <monty@xiph.org>