[FFmpeg-devel] AMR-NB decoder

Colin McQuillan m.niloc
Thu Aug 13 10:33:49 CEST 2009


2009/8/13 Michael Niedermayer <michaelni at gmx.at>:
> On Wed, Aug 12, 2009 at 11:40:59PM +0100, Robert Swain wrote:
>> Hello,
>>
>> 2009/8/10 Colin McQuillan <m.niloc at googlemail.com>:
>> > Reynaldo, Robert, could you review your parts of this patch please? I
>> > checked the QCELP ref decoder before writing the comment.
>> >
>> > 2009/8/10 Michael Niedermayer <michaelni at gmx.at>:
>> >> On Mon, Aug 10, 2009 at 08:42:53AM +0100, Colin McQuillan wrote:
>> >>> 2009/8/9 M?ns Rullg?rd <mans at mansr.com>:
>> >>> > Colin McQuillan <m.niloc at googlemail.com> writes:
>> >>> >
>> >>> >> 2009/8/8 Michael Niedermayer <michaelni at gmx.at>:
>> >>> >>> On Sat, Aug 08, 2009 at 04:09:39PM +0100, Colin McQuillan wrote:
>> >>> >>>> 2009/8/8 Michael Niedermayer <michaelni at gmx.at>:
>> >>> >>>> > On Fri, Aug 07, 2009 at 08:23:53PM +0100, Colin McQuillan wrote:
>> >>> >>>> >> 2009/8/6 Michael Niedermayer <michaelni at gmx.at>:
>> >>> >>>> >> > On Wed, Aug 05, 2009 at 05:51:36PM +0100, Colin McQuillan wrote:
>> >>> >>>> >> >> Attached is a patch for an AMR-NB decoder.
>> >>> >>>>
>> >>> >>>> [...]
>> >>> >>>>
>> >>> >>>> >> > that should e a seperate patch
>> >>> >>>> >>
>> >>> >>>> >> I'll leave this one until I investigate a version for sparse vectors. Attached:
>> >>> >>>> >>
>> >>> >>>> >> 1. Helper functions for gain control in floating-point codecs
>> >>> >>>> >> I couldn't find a similar fixed point function to copy the function name.
>> >>> >>>> >>
>> >>> >>>> >> 2. Floating-point version of ff_acelp_high_pass_filter
>> >>> >>>> >
>> >>> >>>> >> ?acelp_vectors.c | ? 22 ++++++++++++++++++++++
>> >>> >>>> >> ?acelp_vectors.h | ? 27 +++++++++++++++++++++++++++
>> >>> >>>> >> ?2 files changed, 49 insertions(+)
>> >>> >>>> >> f1abbee9b62c1779fd5fb1c634d4ab4294d8611d ?get-set-energyf.patch
>> >>> >>>> >> Index: libavcodec/acelp_vectors.c
>> >>> >>>> >> ===================================================================
>> >>> >>>> >> --- libavcodec/acelp_vectors.c ? ? ? ?(revision 19606)
>> >>> >>>> >> +++ libavcodec/acelp_vectors.c ? ? ? ?(working copy)
>> >>> >>>> >> @@ -155,3 +155,25 @@
>> >>> >>>> >> ? ? ? ? ?out[i] = weight_coeff_a * in_a[i]
>> >>> >>>> >> ? ? ? ? ? ? ? ? + weight_coeff_b * in_b[i];
>> >>> >>>> >> ?}
>> >>> >>>> >> +
>> >>> >>>> >> +float ff_energyf(const float *v, int length)
>> >>> >>>> >> +{
>> >>> >>>> >> + ? ?float sum = 0;
>> >>> >>>> >> + ? ?int i;
>> >>> >>>> >> +
>> >>> >>>> >> + ? ?for (i = 0; i < length; i++)
>> >>> >>>> >> + ? ? ? ?sum += v[i] * v[i];
>> >>> >>>> >> +
>> >>> >>>> >> + ? ?return sum;
>> >>> >>>> >> +}
>> >>> >>>> >
>> >>> >>>> > ff_dot_productf)(
>> >>> >>>>
>> >>> >>>> Do you mean that ff_energyf is redundant? I've taken it out.
>> >>> >>>
>> >>> >>> hmm well, as you say it that way, ff_energyf() could be faster due to
>> >>> >>> fewer mem reads, if that is te case in practice it could be kept
>> >>> >>
>> >>> >> ff_energyf is reliably 4% faster in my test, so I'll add it back in.
>> >>> >
>> >>> > That function has high simdicity so it should be added to dsputil and
>> >>> > simdified.
>> >>>
>> >>> I'll try, but I didn't mean to imply that energy calculations are
>> >>> critical to performance. The slow parts of the AMR decoder are the IIR
>> >>> and FIR filters, which are already in celp_filters.c.
>> >>
>> >> if the SIMD energy is not reaching an overall (whole codec) 0.1% speedup over
>> >> using a more generic SIMD dot product then its probably not worth it and
>> >> could be ommited
>> >
>> > Great! Then I'll leave out ff_energyf, and avoid using "length" in the comments.
>> >
>> > [...]
>> >
>> >> alignment requirements are supposed to be written liks:
>> >> void ff_vp3_idct_put_c(uint8_t *dest/*align 8*/, int line_size, DCTELEM *block/*align 16*/);
>> >> also "/*" is not doxygen compatible and what the function does should be
>> >> more verbosely described, energy isnt a mathematically clear term, dot
>> >> product and sum or squares are.
>> >>
>> >
>> > Changed.
>>
>> The only thing I don't like is the ff_scale_to() function name. I
>> wouldn't know what it did without reading the description. I know a
>> distaste for the use of 'energy' for a generic function has been
>> expressed but I'd understand something like ff_acelp_scale_energy().
>> Does anyone have any better suggestions? Reynaldo? Michael? Colin?
>
> if i remember what the function did ...
>
> scale_vector_to_given_sum_of_squares()
>
> its a little long though ...

Changed
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