Add UMA stats for audio/video containers.

media/filters/ffmpeg_glue.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/filters/ffmpeg_glue.h"
 
 #include "base/lazy_instance.h"
 #include "base/logging.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/synchronization/lock.h"
+#include "media/base/container_names.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 
 namespace media {
 
 // Internal buffer size used by AVIO for reading.
 // TODO(dalecurtis): Experiment with this buffer size and measure impact on
 // performance.  Currently we want to use 32kb to preserve existing behavior
 // with the previous URLProtocol based approach.
 enum { kBufferSize = 32 * 1024 };
 
@@ skipping 96 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(FFmpegInitializer);
 };
 
 void FFmpegGlue::InitializeFFmpeg() {
   static base::LazyInstance<FFmpegInitializer>::Leaky li =
       LAZY_INSTANCE_INITIALIZER;
   CHECK(li.Get().initialized());
 }
 
 FFmpegGlue::FFmpegGlue(FFmpegURLProtocol* protocol)
-    : open_called_(false) {
+    : open_called_(false),
+      protocol_(protocol) {
   InitializeFFmpeg();
 
   // Initialize an AVIOContext using our custom read and seek operations.  Don't
   // keep pointers to the buffer since FFmpeg may reallocate it on the fly.  It
   // will be cleaned up
   format_context_ = avformat_alloc_context();
   avio_context_.reset(avio_alloc_context(
       static_cast<unsigned char*>(av_malloc(kBufferSize)), kBufferSize, 0,
       protocol, &AVIOReadOperation, NULL, &AVIOSeekOperation));
 
@@ skipping 11 matching lines @@
   format_context_->pb = avio_context_.get();
 }
 
 bool FFmpegGlue::OpenContext() {
   DCHECK(!open_called_) << "OpenContext() should't be called twice.";
 
   // If avformat_open_input() is called we have to take a slightly different
   // destruction path to avoid double frees.
   open_called_ = true;
 
+  // Attempt to recognize the container by looking at the first few bytes of the
+  // stream. The stream position is left unchanged.
+  int64 pos;
+  scoped_ptr<uint8[]> buffer(new uint8[8192]);
+
+  protocol_->GetPosition(&pos);

[acolwell GONE FROM CHROMIUM, 2013/05/18 01:22:09]

nit: I think you can use avio_context_->opaque to retrieve the protocol pointer.
It might be better to do that instead so protocol_ and avio_context_ can't get
out of sync.

It might even be worth using avio_tell(), avio_seek(), and avio_read() here so
you don't even have to worry about FFmpegURLProtocol.

[jrummell, 2013/05/22 18:27:39]

Done.

+  protocol_->SetPosition(0);
+  int numRead = protocol_->Read(8192, buffer.get());
+  protocol_->SetPosition(pos);
+  if (numRead > 0) {
+    // < 0 means Read failed
+    container_names::FFmpegContainerName container =
+        container_names::DetermineContainer(buffer.get(), numRead);
+    UMA_HISTOGRAM_SPARSE_SLOWLY("Media.DetectedContainer", container);
+  }
+
   // By passing NULL for the filename (second parameter) we are telling FFmpeg
   // to use the AVIO context we setup from the AVFormatContext structure.
   return avformat_open_input(&format_context_, NULL, NULL, NULL) == 0;
 }
 
 FFmpegGlue::~FFmpegGlue() {
   // In the event of avformat_open_input() failure, FFmpeg may sometimes free
   // our AVFormatContext behind the scenes, but leave the buffer alive.  It will
   // helpfully set |format_context_| to NULL in this case.
   if (!format_context_) {
@@ skipping 27 matching lines @@
         avcodec_close(stream->codec);
       }
     }
   }
 
   avformat_close_input(&format_context_);
   av_free(avio_context_->buffer);
 }
 
 }  // namespace media