Fix compilation of openboard against ffmpeg 7

Package: openboard
Version: 1.6.4+dfsg-1

The source code of openboardis incompatible with the current version of FFmpeg 
7, leading to a crash when trying to compile against it.
The attached patch fixes the issues, allowing successful compilation.

I am using Ubuntu 24.04 and Debian Unstable.

diff -Nru openboard-1.6.4.orig/src/podcast/ffmpeg/UBFFmpegVideoEncoder.cpp 
openboard-1.6.4/src/podcast/ffmpeg/UBFFmpegVideoEncoder.cpp
--- openboard-1.6.4.orig/src/podcast/ffmpeg/UBFFmpegVideoEncoder.cpp    
2022-10-04 05:51:41
+++ openboard-1.6.4/src/podcast/ffmpeg/UBFFmpegVideoEncoder.cpp 2024-09-05 
11:03:47
@@ -443,7 +443,7 @@
         }
 
         // Buffer for resampled/converted audio
-        mAudioOutBuffer = av_audio_fifo_alloc(c->sample_fmt, c->channels, 
c->frame_size);
+        mAudioOutBuffer = av_audio_fifo_alloc(c->sample_fmt, 
c->ch_layout.nb_channels, c->frame_size);
     }
 
 
@@ -563,7 +563,7 @@
     int outSamplesLineSize;
 
     ret = av_samples_alloc_array_and_samples(&outSamples, &outSamplesLineSize,
-                                             codecContext->channels, 
outSamplesCount,
+                                             
codecContext->ch_layout.nb_channels, outSamplesCount,
                                              codecContext->sample_fmt, 0);
     if (ret < 0) {
         qWarning() << "Could not allocate audio samples" << 
avErrorToQString(ret);