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• libavformat fails to link on Macos

  24 avril 2022, par Bilal Shafi

  I'm trying to go through an ffmpeg tutorial however when I try to build my project I get the following error. I initialy thought that cmake's find_path and find_library was linking the wrong files Mark Setchell showed that this was not the case. Now I'm not sure why the linker errors are occurring. Here is the minimum example that fails to compile and the aforementioned error.

  


  [build] [1/1 100% :: 0.076] Linking CXX executable example
[build] FAILED: example 
[build] : && /usr/bin/clang++ -g -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX12.1.sdk -Wl,-search_paths_first -Wl,-headerpad_max_install_names -L/usr/local/opt/llvm/lib CMakeFiles/example.dir/main.cpp.o -o example  /usr/local/lib/libavformat.dylib && :
[build] Undefined symbols for architecture x86_64:
[build]   "avformat_open_input(AVFormatContext**, char const*, AVInputFormat const*, AVDictionary**)", referenced from:
[build]       _main in main.cpp.o
[build]   "avformat_free_context(AVFormatContext*)", referenced from:
[build]       _main in main.cpp.o
[build]   "avformat_alloc_context()", referenced from:
[build]       _main in main.cpp.o
[build] ld: symbol(s) not found for architecture x86_64
[build] clang: error: linker command failed with exit code 1 (use -v to see invocation)
[build] ninja: build stopped: subcommand failed.


  


  CMakeLists.txt :

  


  cmake_minimum_required(VERSION 3.21)
set(CMAKE_CXX_STANDARD 17)


find_path(AVFORMAT_INCLUDE_DIRS libavformat/avformat.h REQUIRED)
find_library(AVFORMAT_LIBRARY avformat REQUIRED)

message(WARNING "AVFORMAT_LIBRARY=" ${AVFORMAT_LIBRARY})
message(WARNING "AVFORMAT_INCLUDE_DIRS=" ${AVFORMAT_INCLUDE_DIRS})

add_executable(example main.cpp)
target_link_libraries(example ${AVFORMAT_LIBRARY})
target_include_directories(example PRIVATE ${AVFORMAT_INCLUDE_DIRS})



  


  main.cpp :

  


  #include <libavformat></libavformat>avformat.h>&#xA;&#xA;#include &#xA;&#xA;&#xA;int main(int argc, char **argv) {&#xA;    if (argc &lt; 2) {&#xA;        printf("example ");&#xA;        exit(EXIT_FAILURE);&#xA;    }&#xA;&#xA;    AVFormatContext *pFormatContext = avformat_alloc_context();&#xA;&#xA;    avformat_open_input(&amp;pFormatContext, argv[1], nullptr, nullptr);&#xA;    printf("Format %s, duration %lld us", pFormatContext->iformat->long_name, pFormatContext->duration);&#xA;&#xA;&#xA;    avformat_free_context(pFormatContext);&#xA;}&#xA;

  


• yt-dlp get audio only link -> ffmpeg piped audio -> ffplay

  5 juin 2022, par james28909

  Ok, i have a perl script that i am trying to figure out why it is throwing an io error. First i use yt-dlg to get the link of only the audio - this works as expected and i can navigate to the link in a browser just fine. then i open a ffmpeg pipe in perl and then try to read the output from ffmpeg and eventually, if i can get this working, i will process the ffmpeg output then send to a named pipe.

  


  the problem comes from the ffmpeg when i am processing the data from the link obtained with yt-dlp, and i think it has to do with my while loop but i am not sure what. i have a named pipe called "input". i summon ffmpeg with the following :

  


  #/usr/bin/perl
use strict;
use warnings;

my $file = /path/to/named/pipe
my $read_len = 1024;

open (my $SOURCE_AUDIO, '-|', "ffmpeg -y -i \'$link\' -map 0 -c copy -ac 2 -f opus -ar 48000 pipe:1");
binmode($SOURCE_AUDIO);

# process the ffmpeg output.i have a function i want to implement here, 
# but i need to be able to parse ffmpeg output in set read lengths

while( read($SOURCE_AUDIO, my $buf, $read_len)){
print $file $buf;
};


  


  but before the end of the playback, somewhere around the end of the audio stream ffmpeg throws errors like this :

  


  [tls @ 0x5d0de00] Error in the pull function..2kbits/s speed=1.21x
[tls @ 0x5d0de00] IO error: Connection reset by peer
[tls @ 0x5d0de00] The specified session has been invalidated for some reason.
    Last message repeated 1 times
https://rr3---sn-(truncated): Input/output error
size=    1021kB time=00:01:18.36 bitrate= 106.7kbits/s speed=1.21x
video:0kB audio:1012kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.808163%


  


  i am not sure what is causing it to end early, or what is causing it to be terminated. i can download the file and re-encode it (if needed) and then play it flawlessly with ffplay, but i cannot, for the life of me, parse ffmpeg output and write it to a named pipe. any help sure would be appreciated. thanks

  


  P.S. i am using latest updated windows 11 and WSL's built in perl :

  


  This is perl 5, version 30, subversion 0 (v5.30.0) built for x86_64-linux-gnu-thread-multi
(with 50 registered patches, see perl -V for more detail)

Copyright 1987-2019, Larry Wall

Perl may be copied only under the terms of either the Artistic License or the
GNU General Public License, which may be found in the Perl 5 source kit.

Complete documentation for Perl, including FAQ lists, should be found on
this system using "man perl" or "perldoc perl".  If you have access to the
Internet, point your browser at http://www.perl.org/, the Perl Home Page.


  


• How do I know if an M3U8 link is from a live transmission or a complete file ?

  17 août 2022, par karurosagu

  This is my problem

  


  I have a downloader app, and one of it's features is downloading M3U8 links using FFmpeg under the hood

  
It only supports a selection of sites and platforms, but i don't want to add support for unknown origin links, not just because it's obviously missing the right headers, cookies and user agent and the user would have to put all of that to work, the main reason is that I don't know how to determine if that link leads to a complete file or if it leads to a live transmission


  This is what happened :

  


  A user of my app gave me a link to test it manually, i ran the code and I noteiced it was taking a lot of time to finish having a decent speed, the file was getting too big, and when i ask him where did the link came from he said it was from a Live TV stream : I had to cancel the download

  


  So, how do i know in FFmpeg if a given M3U8 link leads to a complete file rather than a live transmission ?