loggerd: fix audio truncation by processing remaining partial frames (#35718)

fix audio truncation by processing remaining partial frames

system/loggerd/video_writer.cc

@@ -198,10 +198,23 @@ void VideoWriter::encode_and_write_audio_frame(AVFrame* frame) {
   audio_pts += audio_codec_ctx->frame_size;
 }
 
+void VideoWriter::process_remaining_audio() {
+  // Process remaining audio samples by padding with silence
+  if (audio_buffer.size() > 0 && audio_buffer.size() < audio_codec_ctx->frame_size) {
+    audio_buffer.resize(audio_codec_ctx->frame_size, 0.0f);
+
+    // Encode final frame
+    audio_frame->pts = audio_pts;
+    float *f_samples = reinterpret_cast<float *>(audio_frame->data[0]);
+    std::copy(audio_buffer.begin(), audio_buffer.end(), f_samples);
+    encode_and_write_audio_frame(audio_frame);
+  }
+}
 
 VideoWriter::~VideoWriter() {
   if (this->remuxing) {
     if (this->audio_codec_ctx) {
+      process_remaining_audio();
       encode_and_write_audio_frame(NULL); // flush encoder
       avcodec_free_context(&this->audio_codec_ctx);
     }

system/loggerd/video_writer.h

@@ -21,6 +21,7 @@ public:
 private:
   void initialize_audio(int sample_rate);
   void encode_and_write_audio_frame(AVFrame* frame);
+  void process_remaining_audio();
 
   std::string vid_path, lock_path;
   FILE *of = nullptr;