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

[Thilo Borgmann]

Am 18.07.16 um 20:12 schrieb Umair Khan:
> 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;
>>>>>> +    }
>>>>>> +    return tmp_code;
>>>>>> +}
>>>>>
>>>>> Is there nothing in get_bits.h that solves that already?
>>>>>
>>>>> -Thilo
>>>>
>>>> I'm not sure. It is just reading the bits in the reverse order. May be
>>>> someone else can help.
>>>
>>> theres asv2_get_bits()
>>> if it works here it could be shared
>>
>> note though asv2_get_bits() is maximum 8 bits, for more bits more
>> table lookups or a bigger table is needed
> 
> What should be the best way to use this function? It is not present in
> any header file.

But in a .c file...

-Thilo