Improve avilib code

[s0m30n3]

For a project of mine, I create an AVI file using my own code.
I'm already using libgpac to create MP4 files so only using libgpac would be quite logic.
The only feature missing in libgpac is adding an AVI subtitle.
Eventually I'll add it but I'm starting with some small commits to minimize regression risk.

Currently, we allocate buffers, we fill data and then we write the full chunk on disk.
I propose to write chunk fields one after another to avoid allocating/freeing memory for each chunk.
I created some helpers and demonstrated their usage reimplementing a function.
If you don't like "if(ret) goto on_error" lines, we can use a macro like CHECK_GOTO(conditon, label).

My ultimate goal is to store all needed informations in avi_t and write the AVI file once for all.
It'll use more memory so I'm not sure whether it's an improvement.

Anyway, I'm open to suggestions.

[jeanlf]

Thanks for looking into this. I doubt storing the entire avi in memory is a good idea. However, using an internal buffer to serialize chunks rather than using file io would be indeed a great improvement, especially for GPAC 0.9.0: for now avi muxer is a sink filter, such a change would make it a true mux filter with redirectable output. Do you think you could try patching the avi writer to write to internal mem and notify the caller through callbacks?

[codecov-io]

Codecov Report

Merging #1218 into master will increase coverage by 0.51%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #1218      +/-   ##
==========================================
+ Coverage   49.79%   50.31%   +0.51%     
==========================================
  Files         323      323              
  Lines      228164   227427     -737     
==========================================
+ Hits       113616   114422     +806     
+ Misses     114548   113005    -1543

Impacted Files	Coverage Δ
src/media_tools/avilib.c	43.06% <0%> (-1.89%)	⬇️
src/ietf/sdp.c	0% <0%> (-66.73%)	⬇️
modules/rtp_in/rtp_stream.c	0% <0%> (-47.32%)	⬇️
src/ietf/rtp.c	32.3% <0%> (-35.61%)	⬇️
modules/rtp_in/sdp_load.c	0% <0%> (-33.85%)	⬇️
src/ietf/rtcp.c	29.85% <0%> (-27.02%)	⬇️
modules/rtp_in/rtp_in.c	10.8% <0%> (-23.38%)	⬇️
modules/rtp_in/sdp_fetch.c	0% <0%> (-20.24%)	⬇️
src/ietf/rtp_depacketizer.c	0% <0%> (-16.33%)	⬇️
modules/rtp_in/rtp_session.c	0% <0%> (-10.21%)	⬇️
... and 101 more

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[jeanlf]

no progress on this and not really the approach we would need, closing.