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

[Michael N. <mic...@gm...>]

On Thu, Mar 19, 2009 at 07:35:49PM -0600, Bob Ingraham wrote:
> 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?)

You shouldnt draw into the internal buffers of libavcodec, it uses them for
predicting future frames. Also you likely want to read the docs about 
get/relealse_buffer()

about postprocessing, theres libpostproc and some filters in mplayers
libmpcodecs like vf_spp, later is significantly slower but higher quality


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct awnser.