Developer Forum

Hello to all,
I have to build a gateway that receives an MPEG-4 (simple profile)
stream at datarate M and, in realtime, recompress it to obtain an
MPEG-4 stream at a lower datarate O < M.
I have written all software to receive and transmit using RTP and
Transport Stream (mux/demix) but I don't know how to recompress without
passing through the decode-encode chain that is very expensive.

Do you know if there is a way to process an MPEG-4 stream to lower the
resolution and bitrate?

Thank you very much,
pankry

There is no other way besides decoding and encoding at a lower resolution.

Or, you could simply drop some full frames and let the decoder handle the loss...


--
Phil Frisbie, Jr.
Hawk Software
http://www.yqcomputer.com/

Decode the huffmann compression of macroblocks, and recompress them with a
different (coarser) quantisation matrix.

There's no need to do the full jpeg IDCT/DCT step (which is the most
costly).

However, let's hope your original stream has enough I-frames, because this
approach may suffer increasing quality loss over a couple of frames.

Nils