Fix FFmpeg4 compilation

Author: NicolasHug

src/torchcodec/_core/Encoder.cpp

@@ -96,33 +96,6 @@ AVSampleFormat findBestOutputSampleFormat(const AVCodec& avCodec) {
   return avCodec.sample_fmts[0];
 }
 
-UniqueAVFrame allocateAVFrame(
-    int numSamples,
-    int sampleRate,
-    int numChannels,
-    AVSampleFormat sampleFormat) {
-  auto avFrame = UniqueAVFrame(av_frame_alloc());
-  TORCH_CHECK(avFrame != nullptr, "Couldn't allocate AVFrame.");
-
-  avFrame->nb_samples = numSamples;
-  avFrame->sample_rate = sampleRate;
-  av_channel_layout_default(&avFrame->ch_layout, numChannels);
-  avFrame->format = sampleFormat;
-  auto status = av_frame_get_buffer(avFrame.get(), 0);
-
-  TORCH_CHECK(
-      status == AVSUCCESS,
-      "Couldn't allocate avFrame's buffers: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-
-  status = av_frame_make_writable(avFrame.get());
-  TORCH_CHECK(
-      status == AVSUCCESS,
-      "Couldn't make AVFrame writable: ",
-      getFFMPEGErrorStringFromErrorCode(status));
-  return avFrame;
-}
-
 } // namespace
 
 AudioEncoder::~AudioEncoder() {}

src/torchcodec/_core/FFMPEGCommon.cpp

@@ -210,6 +210,33 @@ void setChannelLayout(
 #endif
 }
 
+UniqueAVFrame allocateAVFrame(
+    int numSamples,
+    int sampleRate,
+    int numChannels,
+    AVSampleFormat sampleFormat) {
+  auto avFrame = UniqueAVFrame(av_frame_alloc());
+  TORCH_CHECK(avFrame != nullptr, "Couldn't allocate AVFrame.");
+
+  avFrame->nb_samples = numSamples;
+  avFrame->sample_rate = sampleRate;
+  setDefaultChannelLayout(avFrame, numChannels);
+  avFrame->format = sampleFormat;
+  auto status = av_frame_get_buffer(avFrame.get(), 0);
+
+  TORCH_CHECK(
+      status == AVSUCCESS,
+      "Couldn't allocate avFrame's buffers: ",
+      getFFMPEGErrorStringFromErrorCode(status));
+
+  status = av_frame_make_writable(avFrame.get());
+  TORCH_CHECK(
+      status == AVSUCCESS,
+      "Couldn't make AVFrame writable: ",
+      getFFMPEGErrorStringFromErrorCode(status));
+  return avFrame;
+}
+
 SwrContext* createSwrContext(
     AVSampleFormat srcSampleFormat,
     AVSampleFormat outSampleFormat,

src/torchcodec/_core/FFMPEGCommon.h

@@ -163,6 +163,12 @@ void setChannelLayout(
     const UniqueAVFrame& srcAVFrame,
     int desiredNumChannels);
 
+UniqueAVFrame allocateAVFrame(
+    int numSamples,
+    int sampleRate,
+    int numChannels,
+    AVSampleFormat sampleFormat);
+
 SwrContext* createSwrContext(
     AVSampleFormat srcSampleFormat,
     AVSampleFormat desiredSampleFormat,