[FFmpeg-trac] #11062(avformat:new): ZMQ protocol throws "lacks prefix"

[FFmpeg]

#11062: ZMQ protocol throws "lacks prefix"
-------------------------------------+-------------------------------------
             Reporter:  Ruben van    |                     Type:  defect
  de Ven                             |
               Status:  new          |                 Priority:  normal
            Component:  avformat     |                  Version:
                                     |  unspecified
             Keywords:  zmq          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:
 Since updating libavformat to 5.1.5 outputting to a zmq stream stopped
 working. See the command below, which is similar to the
 [https://ffmpeg.org/ffmpeg-protocols.html#zmq protocols documentation].
 The error is:

 {{{
 % ffmpeg -re -i ~/input.m4v  -c:v libx264 -f mpegts
 zmq:tcp://0.0.0.0:5555

 [zmq @ 0x55986eddddc0] URL tcp://0.0.0.0:5556 lacks prefix
 zmq:tcp://0.0.0.0:5556: Invalid argument
 }}}


 I traced the message to the commit
 [https://git.ffmpeg.org/gitweb/ffmpeg.git/commitdiff/8dc091daee4532264c8c06e5a081d35b8892ba18
 8dc091daee4532264c8c06e5a081d35b8892ba18]

 This seems to be the offending line:

 {{{
 if (av_strstart(uri, "zmq:", &uri)) {
 }}}

 From my limited understanding of the
 [https://ffmpeg.org/doxygen/0.6/avstring_8c.html av_string docs], should
 this not be a negated statement as the uri should _always_ be prefixed
 with "zmq:"?


 How to reproduce:
 {{{
 % ffmpeg -re -i ~/input.m4v  -c:v libx264 -f mpegts
 zmq:tcp://0.0.0.0:5555
 ffmpeg version 5.1.5-0+deb12u1 Copyright (c) 2000-2024 the FFmpeg
 developers
 built with gcc 12 (Debian 12.2.0-14)
 }}}

 Downgrading to libavformat 5.1.4 fixes the issue.

 Let me know if you need any additional info.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11062>
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