2 files changed, 5 insertions, 2 deletions
diff --git a/src/codecs/include/codec.hpp b/src/codecs/include/codec.hpp
index 36dda8ff..8aa391b6 100644
--- a/src/codecs/include/codec.hpp
+++ b/src/codecs/include/codec.hpp
@@ -49,6 +49,8 @@ class IStream {
 
   virtual auto CurrentPosition() -> int64_t = 0;
 
+  virtual auto Size() -> std::optional<int64_t> = 0;
+
   /*
    * Called by codecs to indicate that they've finished parsing any header data
    * within this stream, and are about to begin decoding.
diff --git a/src/codecs/mad.cpp b/src/codecs/mad.cpp
index 247e33bc..f36636a1 100644
--- a/src/codecs/mad.cpp
+++ b/src/codecs/mad.cpp
@@ -109,8 +109,9 @@ auto MadMp3Decoder::OpenStream(std::shared_ptr<IStream> input)
   auto vbr_length = GetVbrLength(header);
   if (vbr_length) {
     output.total_samples = vbr_length.value() * channels;
-  } else {
-    // FIXME: calculate length using the filesize, assuming CBR.
+  } else if (input->Size() && header.bitrate > 0) {
+    auto cbr_length = input->Size().value() / (header.bitrate / 8);
+    output.total_samples = cbr_length * output.sample_rate_hz * channels;
   }
   return output;
 }