- Mar 11, 2011
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Jean-Marc Valin authored
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- Feb 16, 2011
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Jean-Marc Valin authored
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- Feb 14, 2011
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Jean-Marc Valin authored
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- Feb 10, 2011
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Jean-Marc Valin authoredGot authorization from all copyright holders
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- Feb 07, 2011
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Jean-Marc Valin authored
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- Feb 06, 2011
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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.
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- Feb 04, 2011
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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.
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- Feb 03, 2011
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Jean-Marc Valin authored
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Jean-Marc Valin authored
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Jean-Marc Valin authored
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Jean-Marc Valin authored
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- Feb 02, 2011
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This stores the caps array in 32nd bits/sample instead of 1/2 bits scaled by LM and the channel count, which is slightly less less accurate for the last two bands, and much more accurate for all the other bands. A constant offset is subtracted to allow it to represent values larger than 255 in 8 bits (the range of unoffset values is 77...304). In addition, this replaces the last modeline in the allocation table with the caps array, allowing the initial interpolation to allocate 8 bits/sample or more, which was otherwise impossible.
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- Feb 01, 2011
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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.
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Previously, we would only split a band if it was allocated more than 32 bits. However, the N=4 codebook can only produce about 22.5 bits, and two N=2 bands combined can only produce 26 bits, including 8 bits for qtheta, so if we wait until we allocate 32, we're guaranteed to fall short. Several of the larger bands come pretty far from filling 32 bits as well, though their split versions will. Greg Maxwell also suggested adding an offset to the threshold to account for the inefficiency of using qtheta compared to another VQ dimension. This patch uses 1 bit as a placeholder, as it's a clear improvement, but we may adjust this later after collecting data on more possibilities over more files.
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- Jan 31, 2011
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Timothy B. Terriberry authored
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.
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Use measured cross-entropy to estimate the real cost of coding qtheta given the allocated qb parameter, instead of the entropy of the PDF. This is generally much lower, and reduces waste at high rates. This patch also removes some intermediate rounding from this computation.
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This extends the previous rebalancing for fine energy in N=1 bands to also allocate extra fine bits for bands that go over their cap.
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- Jan 30, 2011
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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).
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- Jan 29, 2011
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Jean-Marc Valin authored
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Jean-Marc Valin authored
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- Jan 26, 2011
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Jean-Marc Valin authored
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- Jan 10, 2011
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Jean-Marc Valin authored
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- Jan 09, 2011
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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().
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- Dec 30, 2010
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cf874373 raised the limit from 7 to 8 for N>1 bands in interp_bits2pulses(), but did not raise the corresponding limits for N=1 bands, or for [un]quant_energy_finalise(). This commit raises all of the limits to the same value, 8.
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This way if a band doesn't get the fine bits we want because it wasn't allocated enough bits to start with, then we will still give it priority for any spare bits after PVQ.
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- Dec 27, 2010
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Jean-Marc Valin authored
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- Dec 19, 2010
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The modeline-bisection and interpolator have used different criteria for the minimum coding threshold since the introduction of the "backwards done" in 405e6a99. This meant that a lower modeline could be selected which the interpolator was never able to get under the maximum allocation. This patch makes the modeline selection search use the same criteria as the interpolator.
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- Dec 18, 2010
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All of our usage of ec_{enc|dec}_bit_prob had the probability of a "one" being a power of two. This adds a new ec_{enc|dec}_bit_logp() function that takes this explicitly into account. It introduces less rounding error than the bit_prob version, does not require 17-bit integers to be emulated by ec_{encode|decode}_bin(), and does not require any multiplies or divisions at all. It is exactly equivalent to ec_encode_bin(enc,_val?0:(1<<_logp)-1,(1<<_logp)-(_val?1:0),1<<_logp) The old ec_{enc|dec}_bit_prob functions are left in place for now, because I am not sure if SILK is still using them or not when combined in Opus.
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- Dec 17, 2010
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Jean-Marc Valin authored
This improves the allocation for 2.5 ms frames.
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The bisection search in compute_allocation() was not using the same method to count psum as interp_bits2pulses, i.e., it did not include the 64*C<<BITRES<<LM allocation ceiling (this adds at most 84 max operations/frame, and so should have a trivial CPU cost). Again, I wouldn't want to try to explain why these are different in a spec, so let's make them the same. In addition, the procedure used to fill in bits1 and bits2 after the bisection search was not the same as the one used during the bisection search. I.e., the if (bits1[j] > 0) bits1[j] += trim_offset[j]; step was not also done for bits2, so bits1[j] + bits2[j] would not be equal to what was computed earlier for the hi line, and would not be guaranteed to be larger than total. We now compute both allocation lines in the same manner, and then obtain bits2 by subtracting them, instead of trying to compute the offset from bits1 up front. Finally, there was nothing to stop a bitstream from boosting a band beyond the number of bits remaining, which means that bits1 would not produce an allocation less than or equal to total, which means that some bands would receive a negative allocation in the decoder when the "left over" negative bits were redistributed to other bands. This patch only adds the dynalloc offset to allocation lines greater than 0, so that an all-zeros floor still exists; the effect is that a dynalloc boost gets linearly scaled between allocation lines 0 and 1, and is constant (like it was before) after that. We don't have to add the extra condition to the bisection search, because it never examines allocation line 0. This re-writes the indexing in the search to make that explicit; it was tested and gives exactly the same results in exactly the same number of iterations as the old search. -
Commit 8e447678 increased the number of cases where we end skipping without explicit signaling. Before, this would cause the bit we reserved for this purpose to either a) get grabbed by some N=1 band to code its sign bits or b) wind up as part of the fine energy at the end. This patch gives it back to the band where we stopped skipping, which is either the first band, or a band that was boosted by dynalloc. This allows the bit to be used for shape coding in that band, and allows the better computation of the fine offset, since the band knows it will get that bit in advance. With this change, we now guarantee that the number of bits allocated by compute_allocation() is exactly equal to the input total, less the bits consumed by skip flags during allocation itself (assuming total was non-negative; for negative total, no bits are emitted, and no bits are allocated).
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- Dec 16, 2010
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Terminate the coding of skip bits at the last dynalloc boosted band. Otherwise the bitstream allows non-sensible behavior by the encoder (dynallocing bits into a band and then skipping it). This reduces skip bit overhead by about 2-3% at moderate bitrates with the current encoder.
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Jean-Marc Valin authored
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Jean-Marc Valin authored
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Excess fractions of a bit can't be re-used in N=1 bands during quant_all_bands() because there's no shape, only a sign bit. This meant that all the fractional bits in these bands accumulated, often up to 5 or 6 bits for stereo, until the first band with N>1, where they were dumped all at once. This patch moves the rebalancing for N=1 bands to interp_bits2pulses() instead, where excess bits still have a chance to be moved into fine energy.
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In commit ffe10574 JM added a "done" flag to the allocation interpolation loop: whenver a band did not have enough bits to pass its threshold for receiving PVQ pulses, all of the rest of band were given just enough bits for fine energy only. This patch implements JM's "backwards done" idea: instead work backwards, dropping bands until the first band that is over the threshold is encountered, and don't artificially reduce the allocation any more after that. This is much more stable: we can continue to signal manual skips if we want to, but we aren't forced to skip a large number of bands because of an isolated hole in he allocation. This makes low-bitrate 120-sample frames much less rough. It also reduces the force skip threshold from alloc_floor+(1<<BITRES)+1 to just alloc_floor+(1<<BITRES), because the former can now cascade to cause many bands to be skipped. The difference here is subtle, and increases signaling overhead by 0.11% of the total bitrate, but Monty confirmed that removing the +1 reduces noise in the bass (i.e., in N=1 bands where such a skip could cascade). Finally the 64*C<<BITRES<<LM ceiling is moved into the bisection search, instead of just being imposed afterwards, again because I wouldn't want to try to explain in a spec why they're different.
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- Dec 15, 2010
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1) Continue to update left and percoeff if we skip all the way to the first band. This doesn't actually matter for correctness, but I don't want to try to explain in a spec why we aren't doing this. 2) Force all the bits in skipped bands to go to fine energy. Before some of them could continue to be given to pulses, even though no pulses would actually be allocate for them. -
The margin of safety was supposed to be 1/8th bit, not 1 bit, and the bit we reserved to terminate skip signalling before was actually 8 bits. This patch updates the margin of safety to the correct value and accounts for the one bit (not 8) needed for skip signalling. It also fixes the remainder calculation in the skip loop to work correctly when start>0.
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Now that manual skipping is in the same loop as forced skipping, there is no reason to do all of one, then all of the other. This ensures we won't propagate bits to bands that have almost nothing later in quant_all_bands() because we didn't have enough bits to signal them skipped.
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