applications/voipstream: Update deprecated FFmpeg API calls with version guards

Modernized FFmpeg API usage in the voipstream application to support
both legacy and current FFmpeg versions while eliminating deprecation
warnings on newer versions.

Changes:
- Added version guards for avcodec_close() calls (deprecated since
  FFmpeg 3.1/libavcodec 58). The function is now only called for
  older FFmpeg versions, as avcodec_free_context() automatically
  closes the codec in newer versions.

- Updated sample format retrieval in VoipStreamSender to handle the
  deprecated 'sample_fmts' field (deprecated since FFmpeg 6.1). The
  code now uses the legacy field for FFmpeg < 6.1 and the new
  avcodec_get_supported_config() API for FFmpeg >= 6.1.

Author: ZoltanBojthe

src/inet/applications/voipstream/AudioOutFile.cc

@@ -203,8 +203,12 @@ bool AudioOutFile::close()
     av_write_trailer(oc);
 
     // close each codec
+#if LIBAVCODEC_VERSION_MAJOR < 58
+    // avcodec_close() is needed for FFmpeg < 3.1 (libavcodec < 58)
     if (audio_st)
         avcodec_close(codecCtx);
+#endif
+    // Note: For FFmpeg >= 3.1, avcodec_free_context() automatically closes the codec
 
     if (!(oc->oformat->flags & AVFMT_NOFILE)) {
         // close the output file
@@ -225,4 +229,3 @@ AudioOutFile::~AudioOutFile()
 }
 
 } // namespace inet
-

src/inet/applications/voipstream/VoipStreamReceiver.cc

@@ -227,7 +227,11 @@ void VoipStreamReceiver::closeConnection()
 {
     if (!curConn.offline) {
         curConn.offline = true;
+#if LIBAVCODEC_VERSION_MAJOR < 58
+        // avcodec_close() is needed for FFmpeg < 3.1 (libavcodec < 58)
         avcodec_close(curConn.decCtx);
+#endif
+        // Note: For FFmpeg >= 3.1, avcodec_free_context() automatically closes the codec
         avcodec_free_context(&curConn.decCtx);
         curConn.outFile.close();
         emit(connStateSignal, -1L); // so that sum() yields the number of active sessions
@@ -284,4 +288,3 @@ void VoipStreamReceiver::finish()
 }
 
 } // namespace inet
-

src/inet/applications/voipstream/VoipStreamSender.cc

@@ -37,7 +37,11 @@ VoipStreamSender::VoipStreamSender()
 VoipStreamSender::~VoipStreamSender()
 {
     if (pEncoderCtx) {
+#if LIBAVCODEC_VERSION_MAJOR < 58
+        // avcodec_close() is needed for FFmpeg < 3.1 (libavcodec < 58)
         avcodec_close(pEncoderCtx);
+#endif
+        // Note: For FFmpeg >= 3.1, avcodec_free_context() automatically closes the codec
         avcodec_free_context(&pEncoderCtx);
     }
     cancelAndDelete(timer);
@@ -179,9 +183,13 @@ void VoipStreamSender::finish()
 {
     outFile.close();
 
+#if LIBAVCODEC_VERSION_MAJOR < 58
+    // avcodec_close() is needed for FFmpeg < 3.1 (libavcodec < 58)
     if (pCodecCtx) {
         avcodec_close(pCodecCtx);
     }
+#endif
+    // Note: For FFmpeg >= 3.1, avcodec_free_context() automatically closes the codec
 
     if (pReSampleCtx) {
         swr_close(pReSampleCtx);
@@ -252,7 +260,22 @@ void VoipStreamSender::openSoundFile(const char *name)
     if (!pCodecEncoder)
         throw cRuntimeError("Codec '%s' not found!", codec);
 
+    // Set sample format - handle deprecated sample_fmts field in newer FFmpeg versions
+#if LIBAVCODEC_VERSION_MAJOR < 61
     pEncoderCtx->sample_fmt = pCodecEncoder->sample_fmts[0];
+#else /* LIBAVCODEC_VERSION_MAJOR < 61 */
+    // For FFmpeg 6.1+, use the new API to get supported sample formats
+    const void *sample_fmts_ptr = nullptr;
+    int num_sample_fmts = 0;
+    err = avcodec_get_supported_config(nullptr, pCodecEncoder, AV_CODEC_CONFIG_SAMPLE_FORMAT,
+                                       0, &sample_fmts_ptr, &num_sample_fmts);
+    if (err >= 0 && num_sample_fmts > 0 && sample_fmts_ptr != nullptr) {
+        const enum AVSampleFormat *sample_fmts = (const enum AVSampleFormat *)sample_fmts_ptr;
+        pEncoderCtx->sample_fmt = sample_fmts[0];
+    } else {
+        throw cRuntimeError("Codec '%s' does not support any sample format!", codec);
+    }
+#endif /* LIBAVCODEC_VERSION_MAJOR < 61 */
 
     if (avcodec_open2(pEncoderCtx, pCodecEncoder, nullptr) < 0)
         throw cRuntimeError("could not open %s encoding codec!", codec);
@@ -571,4 +594,3 @@ void VoipStreamSender::resampleFrame(const uint8_t **in_data, int in_nb_samples)
 }
 
 } // namespace inet
-