[FFmpeg-soc] [soc] libavsequencer [PATCH] Initial implementation of main AVSequencer public API header file

[Sebastian Vater]

Reimar Döffinger a écrit :
> On Sat, Jul 10, 2010 at 07:24:56PM +0200, Vitor Sessak wrote:
>   
>> On 07/10/2010 07:00 PM, Justin Ruggles wrote:
>>     
>>> Sebastian Vater wrote:
>>>
>>>       
>>>> +    /** Default volume boost level. 65536 equals to 100% which
>>>> +       means no boost.  */
>>>> +    uint32_t volume_boost;
>>>> [...]
>>>> +    /** The current volume boost level. 65536 equals to 100% which
>>>> +       means no boost.  */
>>>> +    uint32_t volume_boost;
>>>> +
>>>> +    /** Left channel volume level. 256 is full volume.  */
>>>> +    uint16_t volume_left;
>>>> +
>>>> +    /** Right channel volume level. 256 is full volume.  */
>>>> +    uint16_t volume_right;
>>>> [...]
>>>> +    /** Current volume for this channel which ranges from 0 (muted)
>>>> +       to 255 (full volume).  */
>>>> +    uint8_t volume;
>>>> +
>>>> +    /** Current stereo panning level for this channel (where 0-127
>>>> +       indicate left stereo channel panning, -128 is central stereo
>>>> +       panning and -127 to -1 indicate right stereo panning).  */
>>>> +    int8_t panning;
>>>>         
>>> Why all these arbitrary integer scales?  Why not floating point or
>>> AVRational instead?
>>>       
>> I don't think floating point is a good idea, let's try to keep
>> everything bit-identical across archs if possible.
>>     

Especially not in data structures which are accessed number of active
channels * mixing rate each second...

>
> You could still go with something more consistent,
> like 16.16 fixed-point or AVRational.
>   

volume_boost is 16.16, I looked at lavu/rational.c it has way to much
multiplications making mixing much slower. I don't want to use
multiply/divide instructions in the main mixing loop routines.

> Particularly
> uint16_t volume_left;
> uint8_t volume;
>   

Changing volume_left & volume_right to 16.16 fixed point would be a good
idea, though.

Normal single channel volume is from 0-255 since that is the volume
range in the trackers.

-- 

Best regards,
                   :-) Basty/CDGS (-: