refactor: simplify MP4 format handling

Replace Mp4Type enum with MIME type string for MP4 format detection:
- Remove Mp4Type enum and its FromStr/Display implementations
- Update new_mp4() to use "audio/mp4" MIME type instead
- Simplify documentation to reflect the change

This change removes unnecessary complexity around MP4 format
variants while maintaining the same functionality through MIME types.

Fixes #612

Author: roderickvd

CHANGELOG.md

@@ -48,6 +48,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Deprecated
 - Deprecated `Sample::zero_value()` function in favor of `Sample::ZERO_VALUE` constant
 
+### Removed
+- Breaking: Removed `Mp4Type` enum in favor of using MIME type string "audio/mp4" for MP4 format detection with `Decoder::new_mp4`.
+
 # Version 0.20.1 (2024-11-08)
 
 ### Fixed

src/decoder/mod.rs

@@ -31,7 +31,6 @@
 use std::fmt;
 #[allow(unused_imports)]
 use std::io::{Read, Seek, SeekFrom};
-use std::str::FromStr;
 use std::time::Duration;
 use std::{error::Error, marker::PhantomData};
 
@@ -129,9 +128,12 @@ pub struct Settings {
     pub(crate) coarse_seek: bool,
     /// Whether to trim frames for gapless playback.
     pub(crate) gapless: bool,
-    /// A hint or extension for the decoder about the format of the stream.
-    /// When known, this can help the decoder to select the correct demuxer.
+    /// An extension hint for the decoder about the format of the stream.
+    /// When known, this can help the decoder to select the correct codec.
     pub(crate) hint: Option<String>,
+    /// An MIME type hint for the decoder about the format of the stream.
+    /// When known, this can help the decoder to select the correct demuxer.
+    pub(crate) mime_type: Option<String>,
     /// Whether the decoder should report as seekable.
     pub(crate) is_seekable: bool,
 }
@@ -143,6 +145,7 @@ impl Default for Settings {
             coarse_seek: false,
             gapless: true,
             hint: None,
+            mime_type: None,
             is_seekable: true,
         }
     }
@@ -252,13 +255,22 @@ impl<R: Read + Seek + Send + Sync + 'static> DecoderBuilder<R> {
 
     /// Sets a format hint for the decoder.
     ///
-    /// When known, this can help the decoder to select the correct demuxer.
+    /// When known, this can help the decoder to select the correct codec.
     /// Common values are "mp3", "wav", "flac", "ogg", etc.
     pub fn with_hint(mut self, hint: &str) -> Self {
         self.settings.hint = Some(hint.to_string());
         self
     }
 
+    /// Sets a mime type hint for the decoder.
+    ///
+    /// When known, this can help the decoder to select the correct demuxer.
+    /// Common values are "audio/mpeg", "audio/vnd.wav", "audio/flac", "audio/ogg", etc.
+    pub fn with_mime_type(mut self, mime_type: &str) -> Self {
+        self.settings.mime_type = Some(mime_type.to_string());
+        self
+    }
+
     /// Configure whether the decoder should report as seekable.
     pub fn with_seekable(mut self, is_seekable: bool) -> Self {
         self.settings.is_seekable = is_seekable;
@@ -665,27 +677,27 @@ impl<R: Read + Seek + Send + Sync + 'static> Decoder<R> {
 
     /// Builds a new decoder with MP4 container format hint.
     ///
-    /// This method provides a hint about the MP4 container type, which may help the decoder
-    /// identify the format more quickly. However, if MP4 decoding fails, other formats
-    /// will still be attempted.
+    /// This method provides a hint that the data is in MP4 container format by setting
+    /// the MIME type to "audio/mp4". This may help the decoder identify the format
+    /// more quickly. However, if MP4 decoding fails, other formats will still be attempted.
     ///
     /// # Errors
     ///
     /// Returns `DecoderError::UnrecognizedFormat` if no suitable decoder was found.
     ///
     /// # Examples
     /// ```no_run
-    /// use rodio::{Decoder, Mp4Type};
+    /// use rodio::Decoder;
     /// use std::fs::File;
     ///
     /// let file = File::open("audio.m4a").unwrap();
-    /// let decoder = Decoder::new_mp4(file, Mp4Type::M4a).unwrap();
+    /// let decoder = Decoder::new_mp4(file).unwrap();
     /// ```
     #[cfg(feature = "symphonia-isomp4")]
-    pub fn new_mp4(data: R, hint: Mp4Type) -> Result<Self, DecoderError> {
+    pub fn new_mp4(data: R) -> Result<Self, DecoderError> {
         match Self::builder()
             .with_data(data)
-            .with_hint(&hint.to_string())
+            .with_mime_type("audio/mp4")
             .build()?
         {
             DecoderOutput::Normal(decoder) => Ok(decoder),
@@ -694,51 +706,6 @@ impl<R: Read + Seek + Send + Sync + 'static> Decoder<R> {
     }
 }
 
-/// Type for specifying MP4 container format variants.
-#[allow(missing_docs)] // Reason: will be removed, see: #612
-#[derive(Debug)]
-pub enum Mp4Type {
-    Mp4,
-    M4a,
-    M4p,
-    M4b,
-    M4r,
-    M4v,
-    Mov,
-}
-
-impl FromStr for Mp4Type {
-    type Err = String;
-
-    fn from_str(input: &str) -> Result<Mp4Type, Self::Err> {
-        match &input.to_lowercase()[..] {
-            "mp4" => Ok(Mp4Type::Mp4),
-            "m4a" => Ok(Mp4Type::M4a),
-            "m4p" => Ok(Mp4Type::M4p),
-            "m4b" => Ok(Mp4Type::M4b),
-            "m4r" => Ok(Mp4Type::M4r),
-            "m4v" => Ok(Mp4Type::M4v),
-            "mov" => Ok(Mp4Type::Mov),
-            _ => Err(format!("{input} is not a valid mp4 extension")),
-        }
-    }
-}
-
-impl fmt::Display for Mp4Type {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let text = match self {
-            Mp4Type::Mp4 => "mp4",
-            Mp4Type::M4a => "m4a",
-            Mp4Type::M4p => "m4p",
-            Mp4Type::M4b => "m4b",
-            Mp4Type::M4r => "m4r",
-            Mp4Type::M4v => "m4v",
-            Mp4Type::Mov => "mov",
-        };
-        write!(f, "{text}")
-    }
-}
-
 impl<R> Iterator for Decoder<R>
 where
     R: Read + Seek,

src/decoder/symphonia.rs

@@ -64,6 +64,9 @@ impl SymphoniaDecoder {
         if let Some(ext) = settings.hint.as_ref() {
             hint.with_extension(ext);
         }
+        if let Some(typ) = settings.mime_type.as_ref() {
+            hint.mime_type(typ);
+        }
         let format_opts: FormatOptions = FormatOptions {
             enable_gapless: settings.gapless,
             ..Default::default()