[Live-devel] JPEGVideoRTPSink and Restart markers

[Cristiano Belloni]

  Il 27/10/2010 09:32, Francisco Feijoo ha scritto:
> Thanks for the quick response Ross,
>
>>
>> Note that the existing "JPEGVideoRTPSink" code already does this. You 
>> should not have to reinvent the wheel here.
>
> I think I should explained this better. I don't know how to obtain the 
> qFactor from one MJPEG image so I'm copying all the values from the 
> original image to the new header. And then 
>  TestJPEGVideoSource::qFactor() returns 255. Maybe this part is wrong 
> and I need to calculate the Q, but how? is there an example of this 
> somewhere?.

Q factor is 255 if the quantization tables are dynamic. You got to 
extract the quantization tables parsing the JPEG header and looking for 
the "DQT" marker(s), [0xFF 0xDB as far as I remember]

>
>>
>> The JPEG transmitting code ("JPEGVideoSource" and "JPEGVideoRTPSink") 
>> currently don't support "Restart Marker Headers" (see RFC 2435, 
>> section 3.1.7).  You will need to update the (definition and 
>> implementation) of these two classes to support them.
>
> Ok, I have been thinking on other possibility. Do you know if is 
> possible to decode de MJPEG image to get a simpler version and remove 
> the restart marker headers?
>
> -- 
> Francisco Feijoo
> Software Engineer
> J2K Video Limited
> W: www.j2kvideo.com <http://www.j2kvideo.com>
>
> El 27/10/2010, a las 02:39, Ross Finlayson escribió:
>
>>> I'm trying to create a rtsp server to stream MJPEG images.
>>
>> Ugh.  JPEG is a *terrible* codec for video streaming.
>>
>>
>>> I have implemented a new TestJPEGFileServerMediaSubsession that 
>>> creates a TestJPEGVideoRTPSink.
>>>
>>> In TestJPEGVideoRTPSink::doSpecialFrameHandling I'm adding the 
>>> quantization tables of the image into the header using 
>>> setSpecialHeaderBytes
>>
>> Note that the existing "JPEGVideoRTPSink" code already does this. You 
>> should not have to reinvent the wheel here.
>>
>>
>>> This is working fine using some JPEG images, but fails with others.
>>>
>>> I'm testing one image that has the marker 0xFF, 0xDD ( Define 
>>> Restart Interval) and I think I have to do something else seeing 
>>> this comment in the code
>>>
>>> // Note: We assume that there are no 'restart markers'
>>>
>>> So, what should I do with images containing restart markers and 
>>> macroblocks?
>>
>> The JPEG transmitting code ("JPEGVideoSource" and "JPEGVideoRTPSink") 
>> currently don't support "Restart Marker Headers" (see RFC 2435, 
>> section 3.1.7).  You will need to update the (definition and 
>> implementation) of these two classes to support them.
>> -- 
>>
>> Ross Finlayson
>> Live Networks, Inc.
>> http://www.live555.com/
>> _______________________________________________
>> live-devel mailing list
>> live-devel at lists.live555.com
>> http://lists.live555.com/mailman/listinfo/live-devel
>
>
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-- 
Belloni Cristiano
Imavis Srl.
www.imavis.com <http://www.imavis.com>
belloni at imavis.com <mailto://belloni@imavis.com>
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