Linphone packages for zoom.us compatibility
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This repository contains linphone packages for Debian, which can be
used to join video conferences hosted on zoom.us.

These are slightly modified versions of the official linphone packages
from Debian 9 (stretch).  (Note that these are OLD packages!  A
slightly newer version of Linphone is available in Debian 10, but I
haven't figured out how to make that version work with H.264 video.  I
haven't had any luck using the latest version of Linphone, either.)

These packages can probably also be compiled for Ubuntu and similar
systems, but you'd need to have the correct versions of various
dependencies (in particular, libsrtp and ffmpeg.)

Quick start:

0. If you're using Debian 10 (buster) or newer:

	cp stretch.list /etc/apt/sources.list.d/
	cp pin-linphone-to-stretch /etc/apt/preferences.d/
	apt update

1. Install the packages:

	apt install                                         \
	   ./liblinphone5_3.6.1-3+bm1_amd64.deb             \
	   ./libmediastreamer-base3_3.6.1-3+bm1_amd64.deb   \
	   ./libmediastreamer-x264_1.4.3-0+bm1_amd64.deb    \
	   ./libortp9_3.6.1-3+bm1_amd64.deb                 \
	   ./linphone_3.6.1-3+bm1_amd64.deb                 \
	   ./linphone-common_3.6.1-3+bm1_all.deb            \
	   ./linphone-nogtk_3.6.1-3+bm1_amd64.deb

2. In your linphone configuration:

   * Disable Opus audio compression.

     Go to Options > Preferences > Codecs, select "Audio codecs" in
     the drop-down, find "opus" in the list and click "Disable".

     (I don't know if this is because of a bug in Debian/Linphone's
     implementation of Opus, or Zoom's implementation, but either way,
     at present, using Opus gives completely garbled and
     unintelligible sound.)

   * Enable H.264 video compression.

     Go to Options > Preferences > Codecs, select "Video codecs" in
     the drop-down, find "H264" in the list and click "Enable".

   * Enable SRTP encryption.

     Go to Options > Preferences > Network settings, and under "Media
     encryption type" select "SRTP".

   * Enable video by default.

     In the Options menu, ensure that "Always start video" is checked.

3. Join a meeting by dialing "sip:<MEETING-ID>@zoomcrc.com".  For
   example, if your meeting ID is "123 456 789", you would dial
   sip:123456789@zoomcrc.com in Linphone.

   This may require the person creating the meeting to have a
   commercial license from Zoom.

   Note that your "current identity" (selected at the bottom of the
   linphone window) determines the name that will be shown to other
   meeting participants.


Troubleshooting
---------------

* It says "User is temporarily unavailable".

  -> Check that "H264" is enabled in Video Codecs, and that "Always
     start video" is checked.

* Connected but sounds like a needle being scratched across a record.

  -> Check that "opus" is disabled in Audio Codecs.

* Connected but no sound at all.

  -> Check that "PCMU", "PCMA", and/or "G722" are enabled in Audio
     Codecs.  You may want to play with these to see which gives the
     best results.

* Connected but gives an error about encryption being required.

  -> Check that Media Encryption Type is set to SRTP.

* It still doesn't work.

  -> Tell your friends to use Jitsi instead.


Changes from the official Debian packages
-----------------------------------------

The only change made to linphone is to enable the use of SRTP, which
was disabled in the official Debian package due to symbol leakage in
libsrtp.

(I'm not sure what exactly the issue is that linphone was trying to
avoid here - which library functions are conflicting with which
others.  The linphone package itself recommends using linphone's fork
of libsrtp instead, but it's not entirely clear which version is
needed.)

Anyway, to work around any possible conflicts, I simply load libsrtp
using dlopen in libortp.  This is a nasty kludge but it seems to work.

In addition to the linphone package itself, H.264 support is provided
by the separate msx264 package.  Note that this package is closely
tied to the libmediastreamer API; msx264-1.4.3 appears to be the
correct version to use with linphone-3.6.1.


Copying
-------

All modifications are licensed under the same terms as linphone itself
(GNU General Public License, version 2 or later.)