FFmpeg

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Author	SHA1	Message	Date
Ben Avison	87552d54d3	armv6: Accelerate ff_fft_calc for general case (nbits != 4) The previous implementation targeted DTS Coherent Acoustics, which only requires nbits == 4 (fft16()). This case was (and still is) linked directly rather than being indirected through ff_fft_calc_vfp(), but now the full range from radix-4 up to radix-65536 is available. This benefits other codecs such as AAC and AC3. The implementaion is based upon the C version, with each routine larger than radix-16 calling a hierarchy of smaller FFT functions, then performing a post-processing pass. This pass benefits a lot from loop unrolling to counter the long pipelines in the VFP. A relaxed calling standard also reduces the overhead of the call hierarchy, and avoiding the excessive inlining performed by GCC probably helps with I-cache utilisation too. I benchmarked the result by measuring the number of gperftools samples that hit anywhere in the AAC decoder (starting from aac_decode_frame()) or specifically in the FFT routines (fft4() to fft512() and pass()) for the same sample AAC stream: Before After Mean StdDev Mean StdDev Confidence Change Audio decode 2245.5 53.1 1599.6 43.8 100.0% +40.4% FFT routines 940.6 22.0 348.1 20.8 100.0% +170.2% Signed-off-by: Martin Storsjö <martin@martin.st>	11 years ago
Martin Storsjö	8b9eba664e	arm: Add VFP-accelerated version of fft16 Before After Mean StdDev Mean StdDev Change This function 1389.3 4.2 967.8 35.1 +43.6% Overall 15577.5 83.2 15400.0 336.4 +1.2% Signed-off-by: Martin Storsjö <martin@martin.st>	12 years ago

Author

SHA1

Message

Date

Ben Avison

87552d54d3

armv6: Accelerate ff_fft_calc for general case (nbits != 4)

The previous implementation targeted DTS Coherent Acoustics, which only
requires nbits == 4 (fft16()). This case was (and still is) linked directly
rather than being indirected through ff_fft_calc_vfp(), but now the full
range from radix-4 up to radix-65536 is available. This benefits other codecs
such as AAC and AC3.

The implementaion is based upon the C version, with each routine larger than
radix-16 calling a hierarchy of smaller FFT functions, then performing a
post-processing pass. This pass benefits a lot from loop unrolling to
counter the long pipelines in the VFP. A relaxed calling standard also
reduces the overhead of the call hierarchy, and avoiding the excessive
inlining performed by GCC probably helps with I-cache utilisation too.

I benchmarked the result by measuring the number of gperftools samples that
hit anywhere in the AAC decoder (starting from aac_decode_frame()) or
specifically in the FFT routines (fft4() to fft512() and pass()) for the
same sample AAC stream:

              Before          After
              Mean   StdDev   Mean   StdDev  Confidence  Change
Audio decode  2245.5 53.1     1599.6 43.8    100.0%      +40.4%
FFT routines  940.6  22.0     348.1  20.8    100.0%      +170.2%

Signed-off-by: Martin Storsjö <martin@martin.st>

11 years ago

Martin Storsjö

8b9eba664e

arm: Add VFP-accelerated version of fft16

Before           After
               Mean    StdDev   Mean    StdDev  Change
This function   1389.3  4.2       967.8  35.1   +43.6%
Overall        15577.5 83.2     15400.0 336.4    +1.2%

Signed-off-by: Martin Storsjö <martin@martin.st>

12 years ago

4 Commits (4327088da355509b9f97e4bdb658456ee56de72b)