Hi,
On 01/07/2011 10:25 PM, Laurent Pinchart wrote:
Hi Mitar,
On Sunday 24 October 2010 17:46:28 Mitar wrote:
<snip>
Otherwise things work as expected. The only thing I noticed is that
with such high resolution and MJPEG encoding decoding time of frames
is quite visible if you want to decode MJPEG on the fly in real-time.
For example, with libv4l decoding of one pixel of MJPEG to BGR24 takes
around 0.025 microseconds on my machine. This is nothing important
with for example 640x480 resolution, it takes around 7680
microseconds, that is 8 milliseconds. But with 2592x1944 this becomes
around 125 milliseconds. So it is impossible to decode stream n the
fly in real-time with 10 FPS which device supports for this resolution
and MJPEG.
Has anybody tried to improve MJPEG support in libv4l? For example by
using ffmpeg MJPEG decoder? They argue it has better performance:
https://roundup.ffmpeg.org/issue1816
You will have to ask that on the linux-media mailing list. I know there was a
mail thread about the same topic recently.
Correct, someone wrote a patch for libv4l to use ffmpeg's jpeg decoder
I nacked this, because ffmpeg is not in all major distributions because
of licensing issues. In the same thread I expressed interest in adding
support to libv4l for using libjpeg to do the decompression of regular
jpeg (we will need to keep the tinyjpeg copy around for special
jpeg variants like pjpg). Note adding libjpeg supports also automatically
adds support for libjpeg-turbo, which is API and even ABI compatible.
Regards,
Hans
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