releasenoteexolmpegts.txt

pnx1500 mpeg2 ts stream demo

                          Release Note for exolMpegTs
                          ======= ==== === ==========

Date: 2005-02-17
===== ==========

Differences from the previous release
----------- ---- --- -------- -------

   ---Completely rewritten.

   ---New option -fgpi allows input from FGPI hardware (using new data format
subtype tsfFgpiTimeStamped). Tested only on hardware supplied courtesy of VCOM.
Other hardware platforms may follow. The STC ("System Time Clock", ie, "our"
MPEG clock) is frequency-adjusted to match the PCR ("Programme Clock Reference",
ie, the clock at the decoder.)

   ---A/V sync also now works when playing from file. (The STC frequency is not
changed, but the PTS's of video and audio packets are passed to the renderers
and interpreted correctly.)

   ---Can send audio to either AC3 or MP3 decoders, under control of options
-ac3 or -mp3.

   ---Uses new tmDemuxMpegTs and tmFgpiWrapper components.

   ---Enables graceful degradation: drops B and P frames without decoding them,
if the decoder can detect a problem.

   ---Renamed from exolDemuxMpegTs.

Known problems with this component
----- -------- ---- ---- ---------

   ---AC3 decoder rejects packets ("PTS expired") if it is given a clock. This
may be a demux problem or a decoder problem.

   ---Decoded AC3 packets arrive at the renderer with excessively varying PTS's.
(This may be the same problem.)

   ---More investigation is needed into the relationship between PCR's and PTS's
in common streams. There seems to be a very low frequency (period 10--20s)
"wave" in this value, with an amplitude of 1/3s.

   ---The video and audio queues are too long: 1/3s. This is to allow for the
wave. Some of the needed "lag" could be moved from the uncompressed domain
(decoder-to-renderer) back into the encoded queues (demux-to-decoder).

   ---The wave seems to have different values, even after averaging over the
10--20s required. This means that frames can be dropped for the first 10--20s of
a new stream, as the demux locks onto it.

Missing functionality
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   ---Dynamic switching of audio decoder is not supported, though the audio
format is available in the PMT.

Untested features
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   ---Needs to be better characterised with more streams.

Date: 2002-03-12
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Differences from the previous release
----------- ---- --- -------- -------

   ---Not applicable. This component is in the first release.

Known Problems with this component
----- -------- ---- ---- ---------

   ---A/V sync and buffering need to be implemented in the application.

Missing functionality
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   ---All functionalities described in the manual and IP brief have been
implemented.

Untested features
-------- --------

   ---Not all the features have been tested thoroughly.