Re: [mpeg2-dev] Decoding MPEG-TS stream

[Bob I. <bo...@br...>]

Good news!

Shortly after I wrote that last email I found that the cause of many (but not all,) of my major artifacts was my coding error in decoding the adaptation field length.

After re-reading the MPEG2 spec, I realized that I was one byte too short in calculating the byte offset of the payload when a adapation field was present in the TS packet. Hence, the frequent major artifacts were a result of one extra byte of data before the actual mpeg2 frame.

So, I am an idiot! How exciting is that? :-)

Anyway, the image is much more stable. However I still get a *lot* of artifacts when displaying a live shot of the ocean waves crashing onto a beach in California. (I work for a satellite company and we have some hi-def, fixed cameras at this particular beach...)

The edges of the waves, along with white caps on the waves definitely cause grief, but the biggest problem is the OSD of the clock-time superimposed on the frames (it changes every second,) - it looks like the time gets washed torwards the shore every time a wave passes through it. Also, the digits of the numbers are supposed to be white and they keep turning rainbow colors...

But, as sanity check, I a comparing the same satellite feed coming through libavcodec versus a commercial mpeg2 receiver, and the mpeg2 receiver has zero-problems with the OSD clock overlay. The time-digits are steady and white and the blockiness of the waves is finer grained.

Michael, I respect your work, knowledge and contributions to ffmpeg and would happy to post a stream capture of the live beach video tomorrow for folks to test with.

Based on the above descripton, do you have any recommendations for tweaking the CodecContext (or applying a post-processing filter to smooth-out the wave edges?)

Best Regards,
Bob Ingraham


----- Original Message -----
From: "Michael Niedermayer" <mic...@gm...>
To: "Bob Ingraham" <bo...@br...>
Cc: lib...@li...
Sent: Thursday, March 19, 2009 6:39:05 PM GMT -07:00 US/Canada Mountain
Subject: Re: [mpeg2-dev] Decoding MPEG-TS stream

On Thu, Mar 19, 2009 at 05:55:09PM -0600, Bob Ingraham wrote:
> Thanks Måns.
> 
> The better result that I am seeking from libmpeg2 is better error detection and concealment.

I belive libmpeg2 does no error concealment


> 
> I don't know if it is better in this way or not, but I have tweaked various CodecContext variables in libavcodec and I am still getting too many artifacts.

This is strange, could you make a short piece of the stream available
for other to check (that is a part which shows too many artifacts)

also you should be able to test the stream with mplayer, mplayer supports
both libmpeg2 and libavcodec

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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