Set pytorch vision decoder probesize for getting stream info based on the...

Set pytorch vision decoder probesize for getting stream info based on the value from decode setting (#6900) (#6950)

Summary:
Pull Request resolved: https://github.com/pytorch/vision/pull/6900



1. Pass along the value of probesize from decode setting.
2. allow pytorch vision decoder to set the probesize for getting stream info

Reviewed By: jdsgomes

Differential Revision: D40967782

fbshipit-source-id: 642ae3b67c50b1fdafc20f9814a52fdf5db527d7
Co-authored-by: Chen Liu <cliu7@meta.com>

torchvision/csrc/io/decoder/decoder.cpp

@@ -312,6 +312,8 @@ bool Decoder::init(
     }
   }
 
+  av_dict_set_int(&options, "probesize", params_.probeSize, 0);
+
   interrupted_ = false;
 
   // ffmpeg avformat_open_input call can hang if media source doesn't respond

torchvision/csrc/io/decoder/defs.h

@@ -213,6 +213,12 @@ struct DecoderParameters {
 
   // Skip packets that fail with EPERM errors and continue decoding.
   bool skipOperationNotPermittedPackets{false};
+
+  // probing size in bytes, i.e. the size of the data to analyze to get stream
+  // information. A higher value will enable detecting more information in case
+  // it is dispersed into the stream, but will increase latency. Must be an
+  // integer not lesser than 32. It is 5000000 by default.
+  int64_t probeSize{5000000};
 };
 
 struct DecoderHeader {