[FFmpeg-devel] [PATCH] avcodec/alsdec: implement floating point decoding

[Umair Khan]

On Tue, Jul 19, 2016 at 5:20 PM, Thilo Borgmann <thilo.borgmann at mail.de> wrote:
> Am 19.07.16 um 09:22 schrieb Umair Khan:
>> On Tue, Jul 19, 2016 at 12:29 PM, Paul B Mahol <onemda at gmail.com> wrote:
>>>
>>> On 7/19/16, Umair Khan <omerjerk at gmail.com> wrote:
>>>> On Tue, Jul 19, 2016 at 3:08 AM, Michael Niedermayer
>>>> <michael at niedermayer.cc> wrote:
>>>>> On Mon, Jul 18, 2016 at 11:42:48PM +0530, Umair Khan wrote:
>>>>>> On Sun, Jul 17, 2016 at 3:38 PM, Michael Niedermayer
>>>>>> <michael at niedermayer.cc> wrote:
>>>>>>> On Sun, Jul 17, 2016 at 11:54:49AM +0200, Michael Niedermayer wrote:
>>>>>>>> On Sun, Jul 17, 2016 at 09:00:48AM +0530, Umair Khan wrote:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> On Sun, Jul 17, 2016 at 12:25 AM, Thilo Borgmann
>>>>>>>>> <thilo.borgmann at mail.de> wrote:
>>>>>>>>>> Hi,
>>>>>>>>>>
>>>>>>>>>>> From 70e65b26cc3f84c9c664c30808b43a5e1cf16eaa Mon Sep 17 00:00:00
>>>>>>>>>>> 2001
>>>>>>>>>>> From: Umair Khan <omerjerk at gmail.com>
>>>>>>>>>>> Date: Sat, 16 Jul 2016 23:52:39 +0530
>>>>>>>>>>> Subject: [PATCH 1/1] avcodec/alsdec: implement floating point
>>>>>>>>>>> decoding
>>>>>>>>>>>
>>>>>>>>>>> It conforms to RM22 version of the reference codec.
>>>>>>>>>>>
>>>>>>>>>>> Signed-off-by: Umair Khan <omerjerk at gmail.com>
>>>>>>>>>>> ---
>>>>>>>>>>>  libavcodec/Makefile           |   2 +-
>>>>>>>>>>>  libavcodec/alsdec.c           | 284
>>>>>>>>>>> +++++++++++++++++++++++++++++++++++++++++-
>>>>>>>>>>>  libavcodec/mlz.c              | 171 +++++++++++++++++++++++++
>>>>>>>>>>>  libavcodec/mlz.h              |  69 ++++++++++
>>>>>>>>>>>  libavutil/softfloat_ieee754.h | 115 +++++++++++++++++
>>>>>>>>>>>  5 files changed, 638 insertions(+), 3 deletions(-)
>>>>>>>>>>>  create mode 100644 libavcodec/mlz.c
>>>>>>>>>>>  create mode 100644 libavcodec/mlz.h
>>>>>>>>>>>  create mode 100644 libavutil/softfloat_ieee754.h
>>>>>>>>>>>
>>>>>>>>>>> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
>>>>>>>>>>> index abef19e..a03adf5 100644
>>>>>>>>>>> --- a/libavcodec/Makefile
>>>>>>>>>>> +++ b/libavcodec/Makefile
>>>>>>>>>>> @@ -163,7 +163,7 @@ OBJS-$(CONFIG_ALAC_DECODER)            +=
>>>>>>>>>>> alac.o alac_data.o alacdsp.o
>>>>>>>>>>>  OBJS-$(CONFIG_ALAC_ENCODER)            += alacenc.o alac_data.o
>>>>>>>>>>>  OBJS-$(CONFIG_ALIAS_PIX_DECODER)       += aliaspixdec.o
>>>>>>>>>>>  OBJS-$(CONFIG_ALIAS_PIX_ENCODER)       += aliaspixenc.o
>>>>>>>>>>> -OBJS-$(CONFIG_ALS_DECODER)             += alsdec.o bgmc.o
>>>>>>>>>>> mpeg4audio.o
>>>>>>>>>>> +OBJS-$(CONFIG_ALS_DECODER)             += alsdec.o bgmc.o mlz.o
>>>>>>>>>>> mpeg4audio.o
>>>>>>>>>>>  OBJS-$(CONFIG_AMRNB_DECODER)           += amrnbdec.o
>>>>>>>>>>> celp_filters.o   \
>>>>>>>>>>>                                            celp_math.o
>>>>>>>>>>> acelp_filters.o \
>>>>>>>>>>>                                            acelp_vectors.o
>>>>>>>>>>>      \
>>>>>>>>>>> diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c
>>>>>>>>>>> index a7e58a2..c710fc3 100644
>>>>>>>>>>> --- a/libavcodec/alsdec.c
>>>>>>>>>>> +++ b/libavcodec/alsdec.c
>>>>>>>>>>> @@ -35,8 +35,11 @@
>>>>>>>>>>>  [...]
>>>>>>>>>>>
>>>>>>>>>>> +/** multiply two softfloats and handle the rounding off
>>>>>>>>>>> + */
>>>>>>>>>>> +static SoftFloat_IEEE754 multiply(SoftFloat_IEEE754 a,
>>>>>>>>>>> SoftFloat_IEEE754 b) {
>>>>>>>>>>> [...]
>>>>>>>>>>
>>>>>>>>>> Why is this in alsdec.c?
>>>>>>>>>
>>>>>>>>> This is not the actual IEEE 754 multiplication. It is as is
>>>>>>>>> mentioned
>>>>>>>>> in the reference spec.
>>>>>>>>> The typical one for 754 floats, I've implemented here separately -
>>>>>>>>> https://github.com/omerjerk/FFmpeg/commit/d6cd4bf66b9da46dd87580d7d974ce44abdcfba2#diff-4dd4b2d8d523f336fbefa96e9252187cR93
>>>>>>>>>
>>>>>>>>>> [...]
>>>>>>>>>>
>>>>>>>>>>> diff --git a/libavcodec/mlz.c b/libavcodec/mlz.c
>>>>>>>>>>> new file mode 100644
>>>>>>>>>>> index 0000000..cb2ed6a
>>>>>>>>>>> --- /dev/null
>>>>>>>>>>> +++ b/libavcodec/mlz.c
>>>>>>>>>>> [...]
>>>>>>>>>>
>>>>>>>>>>> +static int input_code(GetBitContext* gb, int len) {
>>>>>>>>>>> +    int tmp_code = 0;
>>>>>>>>>>> +    int i;
>>>>>>>>>>> +    for (i = 0; i < len; ++i) {
>>>>>>>>>>> +        tmp_code += get_bits1(gb) << i;
>                              |=
> should be better.
>
>>>>>>>>>>> +    }
>>>>>>>>>>> +    return tmp_code;
>>>>>>>>>>> +}
>
> Also, you could revert it byte-wise using ff_revert[]... if len is often bigger
> than 8 that might be worth it.

I didn't get you.
I tried logging that variable and len is always greater than 8. So
what should we go with?
It was 9 or 10 for the file I ran. And going with the logic of lzw, it
will hardly be greater than 11 ever.

-Umair