8 files changed, 44 insertions, 8 deletions

diff --git a/src/codecs/dr_flac.cpp b/src/codecs/dr_flac.cpp
index 9341e938..939705ad 100644
--- a/src/codecs/dr_flac.cpp
+++ b/src/codecs/dr_flac.cpp
@@ -97,6 +97,13 @@ auto DrFlacDecoder::OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
       .sample_rate_hz = static_cast<uint32_t>(flac_->sampleRate),
       .total_samples = flac_->totalPCMFrameCount * flac_->channels,
   };
+
+  if (input->Size() && format.total_samples) {
+    double sample_size = *(input->Size()) * 8.0 / *(format.total_samples);
+    format.bitrate_kbps = static_cast<uint32_t>(
+        flac_->sampleRate * flac_->channels * sample_size / 1024);
+  }
+
   return format;
 }
 
diff --git a/src/codecs/include/codec.hpp b/src/codecs/include/codec.hpp
index 4d588a98..6ff7a267 100644
--- a/src/codecs/include/codec.hpp
+++ b/src/codecs/include/codec.hpp
@@ -106,6 +106,7 @@ class ICodec {
     uint8_t num_channels;
     uint32_t sample_rate_hz;
     std::optional<uint32_t> total_samples;
+    std::optional<uint32_t> bitrate_kbps;
 
     bool operator==(const OutputFormat&) const = default;
   };
diff --git a/src/codecs/include/mad.hpp b/src/codecs/include/mad.hpp
index f45b5331..e28e32c8 100644
--- a/src/codecs/include/mad.hpp
+++ b/src/codecs/include/mad.hpp
@@ -36,7 +36,7 @@ class MadMp3Decoder : public ICodec {
   MadMp3Decoder& operator=(const MadMp3Decoder&) = delete;
 
  private:
-  auto SkipID3Tags(IStream& stream) -> void;
+  auto SkipID3Tags(IStream& stream) -> std::optional<uint32_t>;
 
   struct VbrInfo {
     uint32_t length;
diff --git a/src/codecs/mad.cpp b/src/codecs/mad.cpp
index af8b3ec1..d823d99d 100644
--- a/src/codecs/mad.cpp
+++ b/src/codecs/mad.cpp
@@ -63,7 +63,7 @@ auto MadMp3Decoder::OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
     -> cpp::result<OutputFormat, ICodec::Error> {
   input_ = input;
 
-  SkipID3Tags(*input);
+  auto id3size = SkipID3Tags(*input);
 
   // To get the output format for MP3 streams, we simply need to decode the
   // first frame header.
@@ -116,6 +116,14 @@ auto MadMp3Decoder::OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
     output.total_samples = cbr_length * output.sample_rate_hz * channels;
   }
 
+  // header.bitrate is only for CBR, but we've calculated total samples for VBR
+  // and CBR, so we can use that to calculate sample size and therefore bitrate.
+  if (id3size && input->Size()) {
+    auto data_size = input->Size().value() - id3size.value();
+    double sample_size = data_size * 8.0 / output.total_samples.value();
+    output.bitrate_kbps = static_cast<uint32_t>(output.sample_rate_hz * channels * sample_size / 1024);
+  }
+
   if (offset > 1 && cbr_length > 0) {
     // Constant bitrate seeking
     uint64_t skip_bytes = header.bitrate * (offset - 1) / 8;
@@ -263,15 +271,15 @@ auto MadMp3Decoder::DecodeTo(std::span<sample::Sample> output)
                     .is_stream_finished = is_eos_};
 }
 
-auto MadMp3Decoder::SkipID3Tags(IStream& stream) -> void {
+auto MadMp3Decoder::SkipID3Tags(IStream& stream) -> std::optional<uint32_t> {
   // First check that the file actually does start with ID3 tags.
   std::array<std::byte, 3> magic_buf{};
   if (stream.Read(magic_buf) != 3) {
-    return;
+    return {};
   }
   if (std::memcmp(magic_buf.data(), "ID3", 3) != 0) {
     stream.SeekTo(0, IStream::SeekFrom::kStartOfStream);
-    return;
+    return {};
   }
 
   // The size of the tags (*not* including the 10-byte header) is located 6
@@ -279,14 +287,17 @@ auto MadMp3Decoder::SkipID3Tags(IStream& stream) -> void {
   std::array<std::byte, 4> size_buf{};
   stream.SeekTo(6, IStream::SeekFrom::kStartOfStream);
   if (stream.Read(size_buf) != 4) {
-    return;
+    return {};
   }
   // Size is encoded with 7-bit ints for some reason.
   uint32_t tags_size = (static_cast<uint32_t>(size_buf[0]) << (7 * 3)) |
                        (static_cast<uint32_t>(size_buf[1]) << (7 * 2)) |
                        (static_cast<uint32_t>(size_buf[2]) << 7) |
                        static_cast<uint32_t>(size_buf[3]);
-  stream.SeekTo(10 + tags_size, IStream::SeekFrom::kStartOfStream);
+
+  auto skip_bytes = 10 + tags_size;
+  stream.SeekTo(skip_bytes, IStream::SeekFrom::kStartOfStream);
+  return skip_bytes;
 }
 
 /*
diff --git a/src/codecs/native.cpp b/src/codecs/native.cpp
index 124434e8..485694d1 100644
--- a/src/codecs/native.cpp
+++ b/src/codecs/native.cpp
@@ -30,6 +30,8 @@ auto NativeDecoder::OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
       .num_channels = 1,
       .sample_rate_hz = 48000,
       .total_samples = {},
+      // sample rate * channels * bits per sample / bits per kb
+      .bitrate_kbps = 48000 * 1 * 16 / 1024,
   };
 }
 
diff --git a/src/codecs/opus.cpp b/src/codecs/opus.cpp
index b5e7c3fc..3b42516b 100644
--- a/src/codecs/opus.cpp
+++ b/src/codecs/opus.cpp
@@ -129,6 +129,12 @@ auto XiphOpusDecoder::OpenStream(std::shared_ptr<IStream> input,
     length = l * 2;
   }
 
+  auto b = op_bitrate(opus_, -1);
+  std::optional<uint32_t> bitrate_kbps;
+  if (b > 0) {
+    bitrate_kbps = b / 1024;
+  }
+
   if (offset && op_pcm_seek(opus_, offset * 48000) != 0) {
     return cpp::fail(Error::kInternalError);
   }
@@ -137,6 +143,7 @@ auto XiphOpusDecoder::OpenStream(std::shared_ptr<IStream> input,
       .num_channels = 2,
       .sample_rate_hz = 48000,
       .total_samples = length,
+      .bitrate_kbps = bitrate_kbps,
   };
 }
 
diff --git a/src/codecs/vorbis.cpp b/src/codecs/vorbis.cpp
index ea33a2af..464aa4a2 100644
--- a/src/codecs/vorbis.cpp
+++ b/src/codecs/vorbis.cpp
@@ -118,6 +118,12 @@ auto TremorVorbisDecoder::OpenStream(std::shared_ptr<IStream> input,
     length = l * info->channels;
   }
 
+  auto b = ov_bitrate(vorbis_.get(), -1);
+  std::optional<uint32_t> bitrate_kbps;
+  if (b > 0) {
+    bitrate_kbps = b / 1024;
+  }
+
   if (offset && ov_time_seek(vorbis_.get(), offset * 1000) != 0) {
     return cpp::fail(Error::kInternalError);
   }
@@ -126,6 +132,7 @@ auto TremorVorbisDecoder::OpenStream(std::shared_ptr<IStream> input,
       .num_channels = static_cast<uint8_t>(info->channels),
       .sample_rate_hz = static_cast<uint32_t>(info->rate),
       .total_samples = length,
+      .bitrate_kbps = bitrate_kbps,
   };
 }
 
diff --git a/src/codecs/wav.cpp b/src/codecs/wav.cpp
index 746f44ca..d80b7e48 100644
--- a/src/codecs/wav.cpp
+++ b/src/codecs/wav.cpp
@@ -216,7 +216,8 @@ auto WavDecoder::OpenStream(std::shared_ptr<IStream> input, uint32_t offset)
 
   output_format_ = {.num_channels = (uint8_t)num_channels_,
                     .sample_rate_hz = samples_per_second,
-                    .total_samples = number_of_samples};
+                    .total_samples = number_of_samples,
+                    .bitrate_kbps = samples_per_second * num_channels_ * bytes_per_sample_ * 8 / 1024};
 
   return output_format_;
 }