From: Antti Palosaari <crope@iki.fi>
To: Antonio Ospite <ao2@ao2.it>, Hans Verkuil <hverkuil@xs4all.nl>
Cc: Andy Walls <awalls@md.metrocast.net>,
linux-media@vger.kernel.org,
Hans Verkuil <hans.verkuil@cisco.com>
Subject: Re: [PATCHv1 02/12] vivid.txt: add documentation for the vivid driver.
Date: Fri, 01 Aug 2014 18:33:26 +0300 [thread overview]
Message-ID: <53DBB346.5060205@iki.fi> (raw)
In-Reply-To: <20140801171957.fe3359ee5a03f7d512de2027@ao2.it>
On 08/01/2014 06:19 PM, Antonio Ospite wrote:
> On Fri, 01 Aug 2014 12:14:15 +0200
> Hans Verkuil <hverkuil@xs4all.nl> wrote:
>
>> On 07/31/2014 09:16 PM, Andy Walls wrote:
>>> On Wed, 2014-07-30 at 16:23 +0200, Hans Verkuil wrote:
>>>> From: Hans Verkuil <hans.verkuil@cisco.com>
>>>>
> [..]
>>>> +- Improve the sinus generation of the SDR radio.
>>>
>>> Maybe a lookup table, containing the first quarter wave of cos() from 0
>>> to pi/2 in pi/200 steps, and then linear interpolation for cos() of
>>> angles in between those steps. You could go with a larger lookup table
>>> with finer grained steps to reduce the approximation errors. A lookup
>>> table with linear interpolation, I would think, requires fewer
>>> mutliplies and divides than the current Taylor expansion computation.
>>
>> Yeah, I had plans for that. There actually is a sine-table already in vivid-tpg.c
>> since I'm using that to implement Hue support.
>>
>
> I don't know what your requirements are here but JFTR there is already a
> simplistic implementation of fixed point operations in
> include/linux/fixp-arith.h I used them in
> drivers/media/usb/gspca/ov534.c for some hue calculation.
I looked that too, but there was very small LUT => very bad resolution.
So I ended up copying sin/cos from cx88 driver (Taylor method).
regards
Antti
--
http://palosaari.fi/
next prev parent reply other threads:[~2014-08-01 15:33 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-30 14:23 [PATCHv1 00/12] vivid: Virtual Video Test Driver Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 01/12] vb2: fix multiplanar read() with non-zero data_offset Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 02/12] vivid.txt: add documentation for the vivid driver Hans Verkuil
2014-07-31 19:16 ` Andy Walls
2014-08-01 10:14 ` Hans Verkuil
2014-08-01 15:19 ` Antonio Ospite
2014-08-01 15:33 ` Antti Palosaari [this message]
2014-08-01 20:50 ` Andy Walls
2014-07-30 14:23 ` [PATCHv1 03/12] vivid: add core driver code Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 04/12] vivid: add the control handling code Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 05/12] vivid: add the video capture and output parts Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 06/12] vivid: add VBI capture and output code Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 07/12] vivid: add the kthread code that controls the video rate Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 08/12] vivid: add a simple framebuffer device for overlay testing Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 09/12] vivid: add the Test Pattern Generator Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 10/12] vivid: add support for radio receivers and transmitters Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 11/12] vivid: add support for software defined radio Hans Verkuil
2014-07-30 14:23 ` [PATCHv1 12/12] vivid: enable the vivid driver Hans Verkuil
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