Tweak StreamReader error messages and tests (#2429)

Summary:
* Update error messages
* Update audio stream tests

Pull Request resolved: https://github.com/pytorch/audio/pull/2429

Reviewed By: carolineechen, nateanl

Differential Revision: D36812769

Pulled By: mthrok

fbshipit-source-id: 7a51d0c4dbae558010d2e59412333e4a7f00d318

test/torchaudio_unittest/io/stream_reader_test.py

@@ -360,6 +360,21 @@ class StreamReaderInterfaceTest(_MediaSourceMixin, TempDirMixin, TorchaudioTestC
             s.seek(-1.0)
 
 
+def _to_fltp(original):
+    """Convert Tensor to float32 with value range [-1, 1]"""
+    denom = {
+        torch.uint8: 2**7,
+        torch.int16: 2**15,
+        torch.int32: 2**31,
+    }[original.dtype]
+
+    fltp = original.to(torch.float32)
+    if original.dtype == torch.uint8:
+        fltp -= 128
+    fltp /= denom
+    return fltp
+
+
 @skipIfNoFFmpeg
 @_media_source
 class StreamReaderAudioTest(_MediaSourceMixin, TempDirMixin, TorchaudioTestCase):
@@ -399,9 +414,15 @@ class StreamReaderAudioTest(_MediaSourceMixin, TempDirMixin, TorchaudioTestCase)
 
         # provide the matching dtype
         self._test_wav(src, original, fmt=fmt)
-        if not self.test_fileobj:
         # use the internal dtype ffmpeg picks
+        if self.test_fileobj:
+            src.seek(0)
         self._test_wav(src, original, fmt=None)
+        # convert to float32
+        expected = _to_fltp(original)
+        if self.test_fileobj:
+            src.seek(0)
+        self._test_wav(src, expected, fmt="fltp")
 
     @nested_params(
         ["int16", "uint8", "int32"],  # "float", "double", "int64"]

torchaudio/csrc/ffmpeg/ffmpeg.cpp

@@ -252,8 +252,10 @@ void init_codec_context(
     AVBufferRefPtr& pHWBufferRef) {
   const AVCodec* pCodec = get_decode_codec(pParams->codec_id, decoder_name);
 
-  if (avcodec_parameters_to_context(pCodecContext, pParams) < 0) {
-    throw std::runtime_error("Failed to set CodecContext parameter.");
+  int ret = avcodec_parameters_to_context(pCodecContext, pParams);
+  if (ret < 0) {
+    throw std::runtime_error(
+        "Failed to set CodecContext parameter: " + av_err2string(ret));
   }
 
 #ifdef USE_CUDA
@@ -273,16 +275,15 @@ void init_codec_context(
     pCodecContext->get_format = get_hw_format;
     // 3. Create HW device context and set to pCodecContext.
     AVBufferRef* hw_device_ctx = nullptr;
-    // TODO: check how to deallocate the context
-    int err = av_hwdevice_ctx_create(
+    ret = av_hwdevice_ctx_create(
         &hw_device_ctx,
         AV_HWDEVICE_TYPE_CUDA,
         std::to_string(device.index()).c_str(),
         nullptr,
         0);
-    if (err < 0) {
+    if (ret < 0) {
       throw std::runtime_error(
-          "Failed to create CUDA device context: " + av_err2string(err));
+          "Failed to create CUDA device context: " + av_err2string(ret));
     }
     assert(hw_device_ctx);
     pCodecContext->hw_device_ctx = av_buffer_ref(hw_device_ctx);
@@ -291,8 +292,10 @@ void init_codec_context(
 #endif
 
   AVDictionary* opts = get_option_dict(decoder_option);
-  if (avcodec_open2(pCodecContext, pCodec, &opts) < 0) {
-    throw std::runtime_error("Failed to initialize CodecContext.");
+  ret = avcodec_open2(pCodecContext, pCodec, &opts);
+  if (ret < 0) {
+    throw std::runtime_error(
+        "Failed to initialize CodecContext: " + av_err2string(ret));
   }
   auto unused_keys = clean_up_dict(opts);
   if (unused_keys.size()) {

torchaudio/csrc/ffmpeg/stream_reader.cpp

@@ -235,8 +235,7 @@ void StreamReader::add_stream(
   // When media source is file-like object, it is possible that source codec is
   // not detected properly.
   if (stream->codecpar->format == -1) {
-    throw std::runtime_error(
-        "Failed to detect the source stream format. Please provide the decoder to use.");
+    throw std::runtime_error("Failed to detect the source stream format.");
   }
 
   if (!processors[i]) {