Gregory Maxwell authored 13 years ago and Jean-Marc Valin committed 13 years ago

non-ascii characters from the source.

Got authorization from all copyright holders

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This fixes a number of issues for platforms with a 16-bit int, but
 by no means all of them.
The type change for ec_window (for platforms where sizeof(size_t)==2)
 will break ABI (but not API) compatibility with libsilk and libopus,
 and reduce speed on x86-64, but allows the code to work in real-mode
 DOS without using the huge memory model, which is useful for testing
 16-bit int compliance.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This unifies the byte buffer, encoder, and decoder into a single
 struct.
The common encoder and decoder functions (such as ec_tell()) can
 operate on either one, simplifying code which uses both.
The precision argument to ec_tell() has been removed.
It now comes in two precisions:
  ec_tell() gives 1 bit precision in two operations, and
  ec_tell_frac() gives 1/8th bit precision in... somewhat more.
ec_{enc|dec}_bit_prob() were removed (they are no longer needed).
Some of the byte buffer access functions were made static and
 removed from the cross-module API.
All of the code in rangeenc.c and rangedec.c was merged into
 entenc.c and entdec.c, respectively, as we are no longer
 considering alternative backends.
rangeenc.c and rangede.c have been removed entirely.

This passes make check, after disabling the modes that we removed
 support for in cf5d3a8c.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

9b34bd83 caused serious regressions for 240-sample frame stereo,
 because the previous qb limit was _always_ hit for two-phase
 stereo.
Two-phase stereo really does operate with a different model (for
 example, the single bit allocated to the side should really
 probably be thought of as a sign bit for qtheta, but we don't
 count it as part of qtheta's allocation).
The old code was equivalent to a separate two-phase offset of 12,
 however Greg Maxwell's testing demonstrates that 16 performs
 best.

Instead of just dumping excess bits into the first band after
 allocation, use them to initialize the rebalancing loop in
 quant_all_bands().
This allows these bits to be redistributed over several bands, like
 normal.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

The previous "dumb cap" of (64<<LM)*(C<<BITRES) was not actually
 achievable by many (most) bands, and did not take the cost of
 coding theta for splits into account, and so was too small for some
 bands.
This patch adds code to compute a fairly accurate estimate of the
 real maximum per-band rate (an estimate only because of rounding
 effects and the fact that the bit usage for theta is variable),
 which is then truncated and stored in an 8-bit table in the mode.

This gives improved quality at all rates over 160 kbps/channel,
 prevents bits from being wasted all the way up to 255 kbps/channel
 (the maximum rate allowed, and approximately the maximum number of
 bits that can usefully be used regardless of the allocation), and
 prevents dynalloc and trim from producing enormous waste
 (eliminating the need for encoder logic to prevent this).

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This patch makes all symbols conditional on whether or not there's
 enough space left in the buffer to code them, and eliminates much
 of the redundancy in the side information.

A summary of the major changes:
* The isTransient flag is moved up to before the the coarse energy.
  If there are not enough bits to code the coarse energy, the flag
   would get forced to 0, meaning what energy values were coded
   would get interpreted incorrectly.
  This might not be the end of the world, and I'd be willing to
   move it back given a compelling argument.
* Coarse energy switches coding schemes when there are less than 15
   bits left in the packet:
  - With at least 2 bits remaining, the change in energy is forced
     to the range [-1...1] and coded with 1 bit (for 0) or 2 bits
     (for +/-1).
  - With only 1 bit remaining, the change in energy is forced to
     the range [-1...0] and coded with one bit.
  - If there is less than 1 bit remaining, the change in energy is
     forced to -1.
    This effectively low-passes bands whose energy is consistently
     starved; this might be undesirable, but letting the default be
     zero is unstable, which is worse.
* The tf_select flag gets moved back after the per-band tf_res
   flags again, and is now skipped entirely when none of the
   tf_res flags are set, and the default value is the same for
   either alternative.
* dynalloc boosting is now limited so that it stops once it's given
   a band all the remaining bits in the frame, or when it hits the
   "stupid cap" of (64<<LM)*(C<<BITRES) used during allocation.
* If dynalloc boosing has allocated all the remaining bits in the
   frame, the alloc trim parameter does not get encoded (it would
   have no effect).
* The intensity stereo offset is now limited to the range
   [start...codedBands], and thus doesn't get coded until after
   all of the skip decisions.
  Some space is reserved for it up front, and gradually given back
   as each band is skipped.
* The dual stereo flag is coded only if intensity>start, since
   otherwise it has no effect.
  It is now coded after the intensity flag.
* The space reserved for the final skip flag, the intensity stereo
   offset, and the dual stereo flag is now redistributed to all
   bands equally if it is unused.
  Before, the skip flag's bit was given to the band that stopped
   skipping without it (usually a dynalloc boosted band).

In order to enable simple interaction between VBR and these
 packet-size enforced limits, many of which are encountered before
 VBR is run, the maximum packet size VBR will allow is computed at
 the beginning of the encoding function, and the buffer reduced to
 that size immediately.
Later, when it is time to make the VBR decision, the minimum packet
 size is set high enough to ensure that no decision made thus far
 will have been affected by the packet size.
As long as this is smaller than the up-front maximum, all of the
 encoder's decisions will remain in-sync with the decoder.
If it is larger than the up-front maximum, the packet size is kept
 at that maximum, also ensuring sync.
The minimum used now is slightly larger than it used to be, because
 it also includes the bits added for dynalloc boosting.
Such boosting is shut off by the encoder at low rates, and so
 should not cause any serious issues at the rates where we would
 actually run out of room before compute_allocation().

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

The mid = (lo+hi)>>1 line in the binary search would allow hi to drop
 down to the same value as lo, meaning the rounding after the search
 would be choosing between the same two values.
This patch changes it to (lo+hi+1)>>1.
This will allow lo to increase up to the value hi, but only in the
 case that we can't possibly allocate enough pulses to meet the
 target number of bits (in which case the rounding doesn't matter).
To pay for the extra add, this moves the +1 in the comparison to bits
 to the other side, which can then be taken outside the loop.
The compiler can't normally do this because it might cause overflow
 which would change the results.

This rarely mattered, but gives a 0.01 PEAQ improvement on 12-byte
 120 sample frames.
It also makes the search process describable with a simple
 algorithm, rather than relying on this particular optimized
 implementation.
I.e., the binary search loop can now be replaced with
  for(lo=0;lo+1<cache[0]&&cache[lo+1]<bits;lo++);
  hi=lo+1;
 and it will give equivalent results.
This was not true before.

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

This allows us to a) not pay a coding cost to avoid skipping bands that are
 stupid to skip (e.g., the first band, or bands that have so few bits that we
 wouldn't redistribute anything) and b) not reserve bits to pay that cost.

This adds some side-information that can be used to change the
threshold freq arbitrarily.

Previous limit was effectively 120.

Uses a scaling factor that gets applied to the allocation matrix.

Conflicts:

	libcelt/celt.c
	libcelt/rate.c
	libcelt/rate.h

Based on 1/2*log2(N)-19/8, but with the 2-bit and 3-bit thresholds
shifted by 2*log2(N)/8 bit and log2(N)/8 bit, respectively.

Fixed a few minor bugs in the process.

Also convert the stereo split code to use log(N)/2 as the bit allocation
offset

Timothy B. Terriberry authored 14 years ago and Jean-Marc Valin committed 14 years ago

The old code allocated too many fine bits to large bands.
New allocations were derived from by numerical optimization using quantization
 MSE sampled from Laplacian distributed random data to within +/- 1 bit for
 N=2...160 and bits per band from 0 to 64.
Those allocations could be modeled with only minor errors using a simple offset
 of 19/8+log2(N), with no bits spent on fine energy when there would not be
 enough bits remaining to code a single pulse.
However, PEAQ testing suggested an offset of 14/8 was better, and that it was
 always worth spending at least one bit on fine energy.

Should eventually allow using 8-bit values for the pulse->bits table.

Adding one more level of band splitting so that splitting at the
PVQ encoding level is no longer necessary.

Uses a triangular PDF for coding the angle.

by POSIX. The other _t types that are not part of the API are still there
for now. Also, got rid of all that was left of the 64-bit types.