Always round up to the next full frame when sizing WebAudio decodes.

media/filters/audio_file_reader.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/audio_file_reader.h"
 
+#include <cmath>
+
 #include "base/logging.h"
 #include "base/time/time.h"
 #include "media/base/audio_bus.h"
 #include "media/ffmpeg/ffmpeg_common.h"
 #include "media/filters/ffmpeg_glue.h"
 
 namespace media {
 
 AudioFileReader::AudioFileReader(FFmpegURLProtocol* protocol)
     : codec_context_(NULL),
       stream_index_(0),
       protocol_(protocol),
       channels_(0),
       sample_rate_(0),
       av_sample_format_(0) {
 }
 
 AudioFileReader::~AudioFileReader() {
   Close();
 }
 
-base::TimeDelta AudioFileReader::duration() const {
-  const AVRational av_time_base = {1, AV_TIME_BASE};
-
-  // Add one microsecond to avoid rounding-down errors which can occur when
-  // |duration| has been calculated from an exact number of sample-frames.
-  // One microsecond is much less than the time of a single sample-frame
-  // at any real-world sample-rate.
-  return ConvertFromTimeBase(
-      av_time_base, glue_->format_context()->duration + 1);
-}
-
-int64 AudioFileReader::number_of_frames() const {
-  return static_cast<int64>(duration().InSecondsF() * sample_rate());
-}
-
 bool AudioFileReader::Open() {
   glue_.reset(new FFmpegGlue(protocol_));
   AVFormatContext* format_context = glue_->format_context();
 
   // Open FFmpeg AVFormatContext.
   if (!glue_->OpenContext()) {
     DLOG(WARNING) << "AudioFileReader::Open() : error in avformat_open_input()";
     return false;
   }
 
@@ skipping 142 matching lines @@
                     << channels_
                     << ", Sample Format: " << av_frame->format << " vs "
                     << av_sample_format_;
 
         // This is an unrecoverable error, so bail out.
         continue_decoding = false;
         break;
       }
 
       // Truncate, if necessary, if the destination isn't big enough.
-      if (current_frame + frames_read > audio_bus->frames())
+      if (current_frame + frames_read > audio_bus->frames()) {
+        DLOG(ERROR) << "Truncating decoded data due to output size.";
         frames_read = audio_bus->frames() - current_frame;
+      }
 
       // Deinterleave each channel and convert to 32bit floating-point with
       // nominal range -1.0 -> +1.0.  If the output is already in float planar
       // format, just copy it into the AudioBus.
       if (codec_context_->sample_fmt == AV_SAMPLE_FMT_FLT) {
         float* decoded_audio_data = reinterpret_cast<float*>(av_frame->data[0]);
         int channels = audio_bus->channels();
         for (int ch = 0; ch < channels; ++ch) {
           float* bus_data = audio_bus->channel(ch) + current_frame;
           for (int i = 0, offset = ch; i < frames_read;
@@ skipping 18 matching lines @@
 
   // Zero any remaining frames.
   audio_bus->ZeroFramesPartial(
       current_frame, audio_bus->frames() - current_frame);
 
   // Returns the actual number of sample-frames decoded.
   // Ideally this represents the "true" exact length of the file.
   return current_frame;
 }
 
+base::TimeDelta AudioFileReader::GetDuration() const {

[Raymond Toy (Google), 2014/03/05 18:28:00]

Why move the code around?

[DaleCurtis, 2014/03/05 19:27:35]

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#Declaration_Order

+  const AVRational av_time_base = {1, AV_TIME_BASE};
+
+  // Add one microsecond to avoid rounding-down errors which can occur when
+  // |duration| has been calculated from an exact number of sample-frames.
+  // One microsecond is much less than the time of a single sample-frame
+  // at any real-world sample-rate.
+  return ConvertFromTimeBase(av_time_base,
+                             glue_->format_context()->duration + 1);
+}
+
+int AudioFileReader::GetNumberOfFrames() const {
+  return static_cast<int>(ceil(GetDuration().InSecondsF() * sample_rate()));
+}
+
 }  // namespace media