From 85e6a0cbeb56df66d4a3e151e1e0fb7c27200bcb Mon Sep 17 00:00:00 2001
From: Thomas Heck <t@b128.net>
Date: Tue, 22 Dec 2020 13:20:55 +0100
Subject: [PATCH] add support for transcoding to mp3

---
 example.audio-conv.yaml |  8 +++++++-
 src/config.rs           | 26 ++++++++++++++++++++------
 src/main.rs             | 23 +++++++++++++++++++++--
 3 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/example.audio-conv.yaml b/example.audio-conv.yaml
index e855202..8d71829 100644
--- a/example.audio-conv.yaml
+++ b/example.audio-conv.yaml
@@ -6,4 +6,10 @@ matches:
     to:
       codec: opus
       bitrate: 160
-      bitrate_type: vbr
+      bitrate_type: vbr # or cbr
+
+    # for mp3:
+    #   codec: mp3
+    #   # one of: 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 or 320
+    #   bitrate: 256
+    #   bitrate_type: vbr # or cbr
diff --git a/src/config.rs b/src/config.rs
index f68410b..6a7b17b 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -25,8 +25,17 @@ pub enum Transcode {
         #[serde(default = "default_opus_bitrate")]
         bitrate: u16,
 
-        #[serde(default = "default_opus_bitrate_type")]
-        bitrate_type: OpusBitrateType,
+        #[serde(default = "bitrate_type_vbr")]
+        bitrate_type: BitrateType,
+    },
+
+    #[serde(rename = "mp3")]
+    Mp3 {
+        #[serde(default = "default_mp3_bitrate")]
+        bitrate: u16,
+
+        #[serde(default = "bitrate_type_vbr")]
+        bitrate_type: BitrateType,
     },
 }
 
@@ -34,6 +43,7 @@ impl Transcode {
     pub fn extension(&self) -> &'static str {
         match self {
             Transcode::Opus { .. } => "opus",
+            Transcode::Mp3 { .. } => "mp3",
         }
     }
 }
@@ -42,21 +52,25 @@ fn default_opus_bitrate() -> u16 {
     160
 }
 
-fn default_opus_bitrate_type() -> OpusBitrateType {
-    OpusBitrateType::Vbr
+fn bitrate_type_vbr() -> BitrateType {
+    BitrateType::Vbr
+}
+
+fn default_mp3_bitrate() -> u16 {
+    256
 }
 
 impl Default for Transcode {
     fn default() -> Self {
         Transcode::Opus {
             bitrate: default_opus_bitrate(),
-            bitrate_type: default_opus_bitrate_type(),
+            bitrate_type: bitrate_type_vbr(),
         }
     }
 }
 
 #[derive(Clone, Debug, Deserialize)]
-pub enum OpusBitrateType {
+pub enum BitrateType {
     #[serde(rename = "cbr")]
     Cbr,
     #[serde(rename = "vbr")]
diff --git a/src/main.rs b/src/main.rs
index f04a358..f8d8b7b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -316,14 +316,33 @@ async fn transcode(
                     encoder.set_property_from_str(
                         "bitrate-type",
                         match bitrate_type {
-                            config::OpusBitrateType::Vbr => "1",
-                            config::OpusBitrateType::Cbr => "0",
+                            config::BitrateType::Vbr => "1",
+                            config::BitrateType::Cbr => "0",
                         },
                     );
 
                     dest_elems.push(encoder);
                     dest_elems.push(gmake("oggmux")?);
                 }
+                config::Transcode::Mp3 {
+                    bitrate,
+                    bitrate_type,
+                } => {
+                    let encoder: Element = gmake("lamemp3enc")?;
+                    // target: "1" = "bitrate"
+                    encoder.set_property_from_str("target", "1");
+                    encoder.set_property("bitrate", &i32::from(*bitrate))?;
+                    encoder.set_property(
+                        "cbr",
+                        match bitrate_type {
+                            config::BitrateType::Vbr => &false,
+                            config::BitrateType::Cbr => &true,
+                        },
+                    )?;
+
+                    dest_elems.push(encoder);
+                    dest_elems.push(gmake("id3v2mux")?);
+                }
             };
 
             let file_dest: gstreamer_base::BaseSink = gmake("filesink")?;