Add YUV420P format support to Streamer API (#2334)

Summary:
This commit adds YUV420P format support to Streamer API.
When the native format of a video is YUV420P, the Streamer will
output Tensor of YUV color channel.

Pull Request resolved: https://github.com/pytorch/audio/pull/2334

Reviewed By: hwangjeff

Differential Revision: D35632916

Pulled By: mthrok

fbshipit-source-id: a7a0078788433060266b8bd3e7cad023f41389f5

torchaudio/csrc/ffmpeg/buffer.cpp

@@ -164,6 +164,55 @@ void AudioBuffer::push_frame(AVFrame* frame) {
 // Modifiers - Push Video
 ////////////////////////////////////////////////////////////////////////////////
 namespace {
+torch::Tensor convert_yuv420p(AVFrame* pFrame) {
+  int width = pFrame->width;
+  int height = pFrame->height;
+
+  auto options = torch::TensorOptions()
+                     .dtype(torch::kUInt8)
+                     .layout(torch::kStrided)
+                     .device(torch::kCPU);
+
+  torch::Tensor y = torch::empty({1, height, width, 1}, options);
+  {
+    uint8_t* tgt = y.data_ptr<uint8_t>();
+    uint8_t* src = pFrame->data[0];
+    int linesize = pFrame->linesize[0];
+    for (int h = 0; h < height; ++h) {
+      memcpy(tgt, src, width);
+      tgt += width;
+      src += linesize;
+    }
+  }
+  torch::Tensor u = torch::empty({1, height / 2, width / 2, 1}, options);
+  {
+    uint8_t* tgt = u.data_ptr<uint8_t>();
+    uint8_t* src = pFrame->data[1];
+    int linesize = pFrame->linesize[1];
+    for (int h = 0; h < height / 2; ++h) {
+      memcpy(tgt, src, width / 2);
+      tgt += width / 2;
+      src += linesize;
+    }
+  }
+  torch::Tensor v = torch::empty({1, height / 2, width / 2, 1}, options);
+  {
+    uint8_t* tgt = v.data_ptr<uint8_t>();
+    uint8_t* src = pFrame->data[2];
+    int linesize = pFrame->linesize[2];
+    for (int h = 0; h < height / 2; ++h) {
+      memcpy(tgt, src, width / 2);
+      tgt += width / 2;
+      src += linesize;
+    }
+  }
+  torch::Tensor uv = torch::cat({u, v}, -1);
+  // Upsample width and height
+  uv = uv.repeat_interleave(2, -2).repeat_interleave(2, -3);
+  torch::Tensor t = torch::cat({y, uv}, -1);
+  return t.permute({0, 3, 1, 2}); // NCHW
+}
+
 torch::Tensor convert_image_tensor(AVFrame* pFrame) {
   // ref:
   // https://ffmpeg.org/doxygen/4.1/filtering__video_8c_source.html#l00179
@@ -189,6 +238,8 @@ torch::Tensor convert_image_tensor(AVFrame* pFrame) {
     case AV_PIX_FMT_GRAY8:
       channel = 1;
       break;
+    case AV_PIX_FMT_YUV420P:
+      return convert_yuv420p(pFrame);
     default:
       throw std::runtime_error(
           "Unexpected format: " + std::string(av_get_pix_fmt_name(format)));

torchaudio/csrc/ffmpeg/prototype.cpp

@@ -193,14 +193,29 @@ std::string get_vfilter_desc(
     // Check other useful formats
     // https://pillow.readthedocs.io/en/stable/handbook/concepts.html#modes
     AVPixelFormat fmt = [&]() {
-      std::string val = format.value();
-      if (val == "RGB")
-        return AV_PIX_FMT_RGB24;
-      if (val == "BGR")
-        return AV_PIX_FMT_BGR24;
-      if (val == "GRAY")
-        return AV_PIX_FMT_GRAY8;
-      throw std::runtime_error("Unexpected format: " + val);
+      const std::map<const std::string, enum AVPixelFormat> valid_choices {
+        {"RGB", AV_PIX_FMT_RGB24},
+        {"BGR", AV_PIX_FMT_BGR24},
+        {"YUV", AV_PIX_FMT_YUV420P},
+        {"GRAY", AV_PIX_FMT_GRAY8},
+      };
+
+      const std::string val = format.value();
+      if (valid_choices.find(val) == valid_choices.end()) {
+        std::stringstream ss;
+        ss << "Unexpected output video format: \"" << val << "\"."
+           << "Valid choices are; ";
+        int i = 0;
+        for (const auto& p : valid_choices) {
+          if (i == 0) {
+            ss << "\"" << p.first << "\"";
+          } else {
+            ss << ", \"" << p.first << "\"";
+          }
+        }
+        throw std::runtime_error(ss.str());
+      }
+      return valid_choices.at(val);
     }();
     components.emplace_back(
         string_format("format=pix_fmts=%s", av_get_pix_fmt_name(fmt)));

torchaudio/prototype/io/streamer.py

@@ -334,6 +334,7 @@ class Streamer:
 
                 - `RGB`: 8 bits * 3 channels
                 - `BGR`: 8 bits * 3 channels
+                - `YUV`: 8 bits * 3 channels
                 - `GRAY`: 8 bits * 1 channels
         """
         i = self.default_video_stream if stream_index is None else stream_index