diff --git a/Cargo.toml b/Cargo.toml
index f71b574..6bc713e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,6 +17,7 @@ codecov = {repository = "sile/hls_m3u8"}
 
 [dependencies]
 trackable = "0.2"
+getset = "0.0.8"
 
 [dev-dependencies]
 clap = "2"
diff --git a/src/media_playlist.rs b/src/media_playlist.rs
index 2f5b7a4..5eca286 100644
--- a/src/media_playlist.rs
+++ b/src/media_playlist.rs
@@ -141,7 +141,7 @@ impl MediaPlaylistBuilder {
 
             // CHECK: `#EXT-X-BYTE-RANGE`
             if let Some(tag) = s.byte_range_tag() {
-                if tag.range().start.is_none() {
+                if tag.to_range().start().is_none() {
                     let last_uri = track_assert_some!(last_range_uri, ErrorKind::InvalidInput);
                     track_assert_eq!(last_uri, s.uri(), ErrorKind::InvalidInput);
                 } else {
diff --git a/src/tags/basic/m3u.rs b/src/tags/basic/m3u.rs
index 2a2c1e2..07f95ec 100644
--- a/src/tags/basic/m3u.rs
+++ b/src/tags/basic/m3u.rs
@@ -1,8 +1,10 @@
-use crate::types::ProtocolVersion;
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
 
+use crate::types::ProtocolVersion;
+use crate::utils::tag;
+use crate::Error;
+
 /// [4.3.1.1. EXTM3U]
 ///
 /// [4.3.1.1. EXTM3U]: https://tools.ietf.org/html/rfc8216#section-4.3.1.1
@@ -27,8 +29,8 @@ impl fmt::Display for ExtM3u {
 impl FromStr for ExtM3u {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert_eq!(s, Self::PREFIX, ErrorKind::InvalidInput);
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        tag(input, Self::PREFIX)?;
         Ok(ExtM3u)
     }
 }
diff --git a/src/tags/basic/version.rs b/src/tags/basic/version.rs
index cfb968d..d81db3f 100644
--- a/src/tags/basic/version.rs
+++ b/src/tags/basic/version.rs
@@ -1,8 +1,10 @@
-use crate::types::ProtocolVersion;
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
 
+use crate::types::ProtocolVersion;
+use crate::utils::tag;
+use crate::Error;
+
 /// [4.3.1.2. EXT-X-VERSION]
 ///
 /// [4.3.1.2. EXT-X-VERSION]: https://tools.ietf.org/html/rfc8216#section-4.3.1.2
@@ -37,10 +39,8 @@ impl fmt::Display for ExtXVersion {
 impl FromStr for ExtXVersion {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
-        let suffix = s.split_at(Self::PREFIX.len()).1;
-        let version = track!(suffix.parse())?;
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let version = tag(input, Self::PREFIX)?.parse()?;
         Ok(ExtXVersion::new(version))
     }
 }
diff --git a/src/tags/master_playlist/i_frame_stream_inf.rs b/src/tags/master_playlist/i_frame_stream_inf.rs
index 8b64a3b..f9e38dc 100644
--- a/src/tags/master_playlist/i_frame_stream_inf.rs
+++ b/src/tags/master_playlist/i_frame_stream_inf.rs
@@ -1,22 +1,35 @@
+use std::fmt;
+use std::str::FromStr;
+
+use getset::{Getters, MutGetters, Setters};
+
 use crate::attribute::AttributePairs;
 use crate::types::{DecimalResolution, HdcpLevel, ProtocolVersion};
 use crate::utils::parse_u64;
-use crate::utils::{quote, unquote};
-use crate::{Error, ErrorKind, Result};
-use std::fmt;
-use std::str::FromStr;
+use crate::utils::{quote, tag, unquote};
+use crate::{Error, ErrorKind};
 
 /// [4.3.4.3. EXT-X-I-FRAME-STREAM-INF]
 ///
 /// [4.3.4.3. EXT-X-I-FRAME-STREAM-INF]: https://tools.ietf.org/html/rfc8216#section-4.3.4.3
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Getters, Setters, MutGetters, Debug, Clone, PartialEq, Eq, Hash)]
+#[get = "pub"]
+#[set = "pub"]
+#[get_mut = "pub"]
 pub struct ExtXIFrameStreamInf {
+    /// The URI, that identifies the associated media playlist.
     uri: String,
+    /// The peak segment bit rate of the variant stream.
     bandwidth: u64,
+    /// The average segment bit rate of the variant stream.
     average_bandwidth: Option<u64>,
+    /// A string that represents the list of codec types contained the variant stream.
     codecs: Option<String>,
+    /// The optimal pixel resolution at which to display all the video in the variant stream.
     resolution: Option<DecimalResolution>,
+    /// The HDCP level of the variant stream.
     hdcp_level: Option<HdcpLevel>,
+    /// The group identifier for the video in the variant stream.
     video: Option<String>,
 }
 
@@ -36,41 +49,6 @@ impl ExtXIFrameStreamInf {
         }
     }
 
-    /// Returns the URI that identifies the associated media playlist.
-    pub const fn uri(&self) -> &String {
-        &self.uri
-    }
-
-    /// Returns the peak segment bit rate of the variant stream.
-    pub const fn bandwidth(&self) -> u64 {
-        self.bandwidth
-    }
-
-    /// Returns the average segment bit rate of the variant stream.
-    pub const fn average_bandwidth(&self) -> Option<u64> {
-        self.average_bandwidth
-    }
-
-    /// Returns a string that represents the list of codec types contained the variant stream.
-    pub fn codecs(&self) -> Option<&String> {
-        self.codecs.as_ref()
-    }
-
-    /// Returns the optimal pixel resolution at which to display all the video in the variant stream.
-    pub const fn resolution(&self) -> Option<DecimalResolution> {
-        self.resolution
-    }
-
-    /// Returns the HDCP level of the variant stream.
-    pub const fn hdcp_level(&self) -> Option<HdcpLevel> {
-        self.hdcp_level
-    }
-
-    /// Returns the group identifier for the video in the variant stream.
-    pub fn video(&self) -> Option<&String> {
-        self.video.as_ref()
-    }
-
     /// Returns the protocol compatibility version that this tag requires.
     pub const fn requires_version(&self) -> ProtocolVersion {
         ProtocolVersion::V1
@@ -105,8 +83,8 @@ impl fmt::Display for ExtXIFrameStreamInf {
 impl FromStr for ExtXIFrameStreamInf {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let input = tag(input, Self::PREFIX)?;
 
         let mut uri = None;
         let mut bandwidth = None;
@@ -115,7 +93,8 @@ impl FromStr for ExtXIFrameStreamInf {
         let mut resolution = None;
         let mut hdcp_level = None;
         let mut video = None;
-        let attrs = AttributePairs::parse(s.split_at(Self::PREFIX.len()).1);
+
+        let attrs = AttributePairs::parse(input);
         for attr in attrs {
             let (key, value) = track!(attr)?;
             match key {
@@ -167,7 +146,7 @@ mod test {
         );
 
         assert_eq!(i_frame_stream_inf.uri(), "foo");
-        assert_eq!(i_frame_stream_inf.bandwidth(), 1000);
+        assert_eq!(*i_frame_stream_inf.bandwidth(), 1000);
         // TODO: test all the optional fields
     }
 
diff --git a/src/tags/master_playlist/media.rs b/src/tags/master_playlist/media.rs
index 7c17b3b..59e2910 100644
--- a/src/tags/master_playlist/media.rs
+++ b/src/tags/master_playlist/media.rs
@@ -1,7 +1,7 @@
 use crate::attribute::AttributePairs;
 use crate::types::{InStreamId, MediaType, ProtocolVersion};
-use crate::utils::{parse_yes_or_no, quote, unquote};
-use crate::{Error, ErrorKind, Result};
+use crate::utils::{parse_yes_or_no, quote, tag, unquote};
+use crate::{Error, ErrorKind};
 use std::fmt;
 use std::str::FromStr;
 
@@ -114,7 +114,7 @@ impl ExtXMediaBuilder {
     }
 
     /// Builds a `ExtXMedia` instance.
-    pub fn finish(self) -> Result<ExtXMedia> {
+    pub fn finish(self) -> crate::Result<ExtXMedia> {
         let media_type = track_assert_some!(self.media_type, ErrorKind::InvalidInput);
         let group_id = track_assert_some!(self.group_id, ErrorKind::InvalidInput);
         let name = track_assert_some!(self.name, ErrorKind::InvalidInput);
@@ -309,11 +309,11 @@ impl fmt::Display for ExtXMedia {
 impl FromStr for ExtXMedia {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let input = tag(input, Self::PREFIX)?;
 
         let mut builder = ExtXMediaBuilder::new();
-        let attrs = AttributePairs::parse(s.split_at(Self::PREFIX.len()).1);
+        let attrs = AttributePairs::parse(input);
         for attr in attrs {
             let (key, value) = track!(attr)?;
             match key {
diff --git a/src/tags/master_playlist/session_data.rs b/src/tags/master_playlist/session_data.rs
index 32b1633..97da40d 100644
--- a/src/tags/master_playlist/session_data.rs
+++ b/src/tags/master_playlist/session_data.rs
@@ -1,17 +1,26 @@
-use crate::attribute::AttributePairs;
-use crate::types::{ProtocolVersion, SessionData};
-use crate::utils::{quote, unquote};
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
 
+use getset::{Getters, MutGetters, Setters};
+
+use crate::attribute::AttributePairs;
+use crate::types::{ProtocolVersion, SessionData};
+use crate::utils::{quote, tag, unquote};
+use crate::{Error, ErrorKind};
+
 /// [4.3.4.4. EXT-X-SESSION-DATA]
 ///
 /// [4.3.4.4. EXT-X-SESSION-DATA]: https://tools.ietf.org/html/rfc8216#section-4.3.4.4
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(Getters, MutGetters, Setters, Debug, Clone, PartialEq, Eq, Hash)]
+#[get = "pub"]
+#[set = "pub"]
+#[get_mut = "pub"]
 pub struct ExtXSessionData {
+    /// The identifier of the data.
     data_id: String,
+    /// The session data.
     data: SessionData,
+    /// The language of the data.
     language: Option<String>,
 }
 
@@ -36,21 +45,6 @@ impl ExtXSessionData {
         }
     }
 
-    /// Returns the identifier of the data.
-    pub const fn data_id(&self) -> &String {
-        &self.data_id
-    }
-
-    /// Returns the session data.
-    pub const fn data(&self) -> &SessionData {
-        &self.data
-    }
-
-    /// Returns the language of the data.
-    pub fn language(&self) -> Option<&String> {
-        self.language.as_ref()
-    }
-
     /// Returns the protocol compatibility version that this tag requires.
     pub const fn requires_version(&self) -> ProtocolVersion {
         ProtocolVersion::V1
@@ -75,14 +69,15 @@ impl fmt::Display for ExtXSessionData {
 impl FromStr for ExtXSessionData {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let input = tag(input, Self::PREFIX)?;
 
         let mut data_id = None;
         let mut session_value = None;
         let mut uri = None;
         let mut language = None;
-        let attrs = AttributePairs::parse(s.split_at(Self::PREFIX.len()).1);
+
+        let attrs = AttributePairs::parse(input);
         for attr in attrs {
             let (key, value) = track!(attr)?;
             match key {
@@ -119,23 +114,38 @@ mod test {
     use super::*;
 
     #[test]
-    fn ext_x_session_data() {
+    fn test_display() {
         let tag = ExtXSessionData::new("foo", SessionData::Value("bar".into()));
         let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",VALUE="bar""#;
-        assert_eq!(text.parse().ok(), Some(tag.clone()));
         assert_eq!(tag.to_string(), text);
-        assert_eq!(tag.requires_version(), ProtocolVersion::V1);
 
         let tag = ExtXSessionData::new("foo", SessionData::Uri("bar".into()));
         let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",URI="bar""#;
-        assert_eq!(text.parse().ok(), Some(tag.clone()));
         assert_eq!(tag.to_string(), text);
-        assert_eq!(tag.requires_version(), ProtocolVersion::V1);
 
         let tag = ExtXSessionData::with_language("foo", SessionData::Value("bar".into()), "baz");
         let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",VALUE="bar",LANGUAGE="baz""#;
-        assert_eq!(text.parse().ok(), Some(tag.clone()));
         assert_eq!(tag.to_string(), text);
+    }
+
+    #[test]
+    fn test_parser() {
+        let tag = ExtXSessionData::new("foo", SessionData::Value("bar".into()));
+        let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",VALUE="bar""#;
+        assert_eq!(text.parse::<ExtXSessionData>().unwrap(), tag);
+
+        let tag = ExtXSessionData::new("foo", SessionData::Uri("bar".into()));
+        let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",URI="bar""#;
+        assert_eq!(text.parse::<ExtXSessionData>().unwrap(), tag);
+
+        let tag = ExtXSessionData::with_language("foo", SessionData::Value("bar".into()), "baz");
+        let text = r#"#EXT-X-SESSION-DATA:DATA-ID="foo",VALUE="bar",LANGUAGE="baz""#;
+        assert_eq!(text.parse::<ExtXSessionData>().unwrap(), tag);
+    }
+
+    #[test]
+    fn test_requires_version() {
+        let tag = ExtXSessionData::new("foo", SessionData::Value("bar".into()));
         assert_eq!(tag.requires_version(), ProtocolVersion::V1);
     }
 }
diff --git a/src/tags/master_playlist/session_key.rs b/src/tags/master_playlist/session_key.rs
index 26cea97..e2d29ba 100644
--- a/src/tags/master_playlist/session_key.rs
+++ b/src/tags/master_playlist/session_key.rs
@@ -1,8 +1,9 @@
-use crate::types::{DecryptionKey, ProtocolVersion};
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
 
+use crate::types::{DecryptionKey, ProtocolVersion};
+use crate::utils::tag;
+
 /// [4.3.4.5. EXT-X-SESSION-KEY]
 ///
 /// [4.3.4.5. EXT-X-SESSION-KEY]: https://tools.ietf.org/html/rfc8216#section-4.3.4.5
@@ -37,13 +38,11 @@ impl fmt::Display for ExtXSessionKey {
 }
 
 impl FromStr for ExtXSessionKey {
-    type Err = Error;
+    type Err = crate::Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
-        let suffix = s.split_at(Self::PREFIX.len()).1;
-        let key = track!(suffix.parse())?;
-        Ok(ExtXSessionKey { key })
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let key = tag(input, Self::PREFIX)?.parse()?;
+        Ok(Self::new(key))
     }
 }
 
diff --git a/src/tags/master_playlist/stream_inf.rs b/src/tags/master_playlist/stream_inf.rs
index 81c8c28..dbeeef9 100644
--- a/src/tags/master_playlist/stream_inf.rs
+++ b/src/tags/master_playlist/stream_inf.rs
@@ -1,12 +1,13 @@
+use std::fmt;
+use std::str::FromStr;
+
 use crate::attribute::AttributePairs;
 use crate::types::{
     ClosedCaptions, DecimalFloatingPoint, DecimalResolution, HdcpLevel, ProtocolVersion,
     SingleLineString,
 };
-use crate::utils::{parse_u64, quote, unquote};
-use crate::{Error, ErrorKind, Result};
-use std::fmt;
-use std::str::FromStr;
+use crate::utils::{parse_u64, quote, tag, unquote};
+use crate::{Error, ErrorKind};
 
 /// [4.3.4.2. EXT-X-STREAM-INF]
 ///
@@ -146,16 +147,15 @@ impl fmt::Display for ExtXStreamInf {
 impl FromStr for ExtXStreamInf {
     type Err = Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        let mut lines = s.splitn(2, '\n');
-        let first_line = lines.next().expect("Never fails").trim_end_matches('\r');
-        let second_line = track_assert_some!(lines.next(), ErrorKind::InvalidInput);
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let mut lines = input.lines();
+        let first_line = lines.next().ok_or(ErrorKind::InvalidInput)?; // TODO!
+        let second_line = lines.next().ok_or(ErrorKind::InvalidInput)?; // TODO!
+
+        tag(first_line, Self::PREFIX)?;
 
-        track_assert!(
-            first_line.starts_with(Self::PREFIX),
-            ErrorKind::InvalidInput
-        );
         let uri = track!(SingleLineString::new(second_line))?;
+
         let mut bandwidth = None;
         let mut average_bandwidth = None;
         let mut codecs = None;
@@ -186,6 +186,7 @@ impl FromStr for ExtXStreamInf {
                 }
             }
         }
+
         let bandwidth = track_assert_some!(bandwidth, ErrorKind::InvalidInput);
         Ok(ExtXStreamInf {
             uri,
diff --git a/src/tags/media_playlist/discontinuity_sequence.rs b/src/tags/media_playlist/discontinuity_sequence.rs
index 07b245b..6619db1 100644
--- a/src/tags/media_playlist/discontinuity_sequence.rs
+++ b/src/tags/media_playlist/discontinuity_sequence.rs
@@ -1,8 +1,8 @@
-use crate::types::ProtocolVersion;
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
-use trackable::error::ErrorKindExt;
+
+use crate::types::ProtocolVersion;
+use crate::utils::tag;
 
 /// [4.3.3.3. EXT-X-DISCONTINUITY-SEQUENCE]
 ///
@@ -39,12 +39,11 @@ impl fmt::Display for ExtXDiscontinuitySequence {
 }
 
 impl FromStr for ExtXDiscontinuitySequence {
-    type Err = Error;
+    type Err = crate::Error;
 
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
-        let seq_num = may_invalid!(s.split_at(Self::PREFIX.len()).1.parse())?;
-        Ok(ExtXDiscontinuitySequence { seq_num })
+    fn from_str(input: &str) -> Result<Self, Self::Err> {
+        let seq_num = tag(input, Self::PREFIX)?.parse().unwrap(); // TODO!
+        Ok(Self::new(seq_num))
     }
 }
 
diff --git a/src/tags/media_segment/byte_range.rs b/src/tags/media_segment/byte_range.rs
index bbc5ab1..9afddfa 100644
--- a/src/tags/media_segment/byte_range.rs
+++ b/src/tags/media_segment/byte_range.rs
@@ -1,39 +1,72 @@
+use std::fmt;
+use std::ops::Deref;
+use std::str::FromStr;
+
+use trackable::error::ErrorKindExt;
+
 use crate::types::{ByteRange, ProtocolVersion};
 use crate::{Error, ErrorKind, Result};
-use std::fmt;
-use std::str::FromStr;
-use trackable::error::ErrorKindExt;
 
 /// [4.3.2.2. EXT-X-BYTERANGE]
 ///
 /// [4.3.2.2. EXT-X-BYTERANGE]: https://tools.ietf.org/html/rfc8216#section-4.3.2.2
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
-pub struct ExtXByteRange {
-    range: ByteRange,
-}
+pub struct ExtXByteRange(ByteRange);
 
 impl ExtXByteRange {
     pub(crate) const PREFIX: &'static str = "#EXT-X-BYTERANGE:";
 
     /// Makes a new `ExtXByteRange` tag.
-    pub const fn new(range: ByteRange) -> Self {
-        ExtXByteRange { range }
+    /// # Example
+    /// ```
+    /// use hls_m3u8::tags::ExtXByteRange;
+    ///
+    /// let byte_range = ExtXByteRange::new(20, Some(5));
+    /// ```
+    pub const fn new(length: usize, start: Option<usize>) -> Self {
+        Self(ByteRange::new(length, start))
     }
 
-    /// Returns the range of the associated media segment.
-    pub const fn range(&self) -> ByteRange {
-        self.range
+    /// Converts the [ExtXByteRange] to a [ByteRange].
+    /// # Example
+    /// ```
+    /// use hls_m3u8::tags::ExtXByteRange;
+    /// use hls_m3u8::types::ByteRange;
+    ///
+    /// let byte_range = ExtXByteRange::new(20, Some(5));
+    /// let range: ByteRange = byte_range.to_range();
+    /// ```
+    pub const fn to_range(&self) -> ByteRange {
+        self.0
     }
 
     /// Returns the protocol compatibility version that this tag requires.
+    /// # Example
+    /// ```
+    /// use hls_m3u8::tags::ExtXByteRange;
+    /// use hls_m3u8::types::ProtocolVersion;
+    ///
+    /// let byte_range = ExtXByteRange::new(20, Some(5));
+    /// assert_eq!(byte_range.requires_version(), ProtocolVersion::V4);
+    /// ```
     pub const fn requires_version(&self) -> ProtocolVersion {
         ProtocolVersion::V4
     }
 }
 
+impl Deref for ExtXByteRange {
+    type Target = ByteRange;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
 impl fmt::Display for ExtXByteRange {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}{}", Self::PREFIX, self.range)
+        write!(f, "{}", Self::PREFIX)?;
+        write!(f, "{}", self.0)?;
+        Ok(())
     }
 }
 
@@ -41,9 +74,30 @@ impl FromStr for ExtXByteRange {
     type Err = Error;
 
     fn from_str(s: &str) -> Result<Self> {
+        // check if the string starts with the PREFIX
         track_assert!(s.starts_with(Self::PREFIX), ErrorKind::InvalidInput);
-        let range = may_invalid!(s.split_at(Self::PREFIX.len()).1.parse())?;
-        Ok(ExtXByteRange { range })
+        let byte_range = s.split_at(Self::PREFIX.len()).1;
+        let tokens = byte_range.splitn(2, '@').collect::<Vec<_>>();
+        if tokens.is_empty() {
+            Err(ErrorKind::InvalidInput)?;
+        }
+
+        let length = tokens[0]
+            .parse()
+            .map_err(|e| ErrorKind::InvalidInput.cause(e))?;
+        let start = {
+            let mut result = None;
+            if tokens.len() == 2 {
+                result = Some(
+                    tokens[1]
+                        .parse()
+                        .map_err(|e| ErrorKind::InvalidInput.cause(e))?,
+                );
+            }
+            result
+        };
+
+        Ok(ExtXByteRange::new(length, start))
     }
 }
 
@@ -52,21 +106,40 @@ mod test {
     use super::*;
 
     #[test]
-    fn ext_x_byterange() {
-        let tag = ExtXByteRange::new(ByteRange {
-            length: 3,
-            start: None,
-        });
-        assert_eq!("#EXT-X-BYTERANGE:3".parse().ok(), Some(tag));
-        assert_eq!(tag.to_string(), "#EXT-X-BYTERANGE:3");
-        assert_eq!(tag.requires_version(), ProtocolVersion::V4);
+    fn test_display() {
+        let byte_range = ExtXByteRange::new(0, Some(5));
+        assert_eq!(byte_range.to_string(), "#EXT-X-BYTERANGE:0@5".to_string());
 
-        let tag = ExtXByteRange::new(ByteRange {
-            length: 3,
-            start: Some(5),
-        });
-        assert_eq!("#EXT-X-BYTERANGE:3@5".parse().ok(), Some(tag));
-        assert_eq!(tag.to_string(), "#EXT-X-BYTERANGE:3@5");
-        assert_eq!(tag.requires_version(), ProtocolVersion::V4);
+        let byte_range = ExtXByteRange::new(99999, Some(2));
+        assert_eq!(
+            byte_range.to_string(),
+            "#EXT-X-BYTERANGE:99999@2".to_string()
+        );
+
+        let byte_range = ExtXByteRange::new(99999, None);
+        assert_eq!(byte_range.to_string(), "#EXT-X-BYTERANGE:99999".to_string());
+    }
+
+    #[test]
+    fn test_parse() {
+        let byte_range = ExtXByteRange::new(99999, Some(2));
+        assert_eq!(
+            byte_range,
+            "#EXT-X-BYTERANGE:99999@2".parse::<ExtXByteRange>().unwrap()
+        );
+
+        let byte_range = ExtXByteRange::new(99999, None);
+        assert_eq!(
+            byte_range,
+            "#EXT-X-BYTERANGE:99999".parse::<ExtXByteRange>().unwrap()
+        );
+    }
+
+    #[test]
+    fn test_deref() {
+        let byte_range = ExtXByteRange::new(0, Some(22));
+
+        assert_eq!(*byte_range.length(), 0);
+        assert_eq!(*byte_range.start(), Some(22));
     }
 }
diff --git a/src/tags/media_segment/discontinuity.rs b/src/tags/media_segment/discontinuity.rs
index d0f3563..9571f2c 100644
--- a/src/tags/media_segment/discontinuity.rs
+++ b/src/tags/media_segment/discontinuity.rs
@@ -1,13 +1,16 @@
-use crate::types::ProtocolVersion;
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::FromStr;
 
+use crate::types::ProtocolVersion;
+use crate::utils::tag;
+use crate::{Error, Result};
+
 /// [4.3.2.3. EXT-X-DISCONTINUITY]
 ///
 /// [4.3.2.3. EXT-X-DISCONTINUITY]: https://tools.ietf.org/html/rfc8216#section-4.3.2.3
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct ExtXDiscontinuity;
+
 impl ExtXDiscontinuity {
     pub(crate) const PREFIX: &'static str = "#EXT-X-DISCONTINUITY";
 
@@ -25,8 +28,9 @@ impl fmt::Display for ExtXDiscontinuity {
 
 impl FromStr for ExtXDiscontinuity {
     type Err = Error;
-    fn from_str(s: &str) -> Result<Self> {
-        track_assert_eq!(s, Self::PREFIX, ErrorKind::InvalidInput);
+
+    fn from_str(input: &str) -> Result<Self> {
+        tag(input, Self::PREFIX)?;
         Ok(ExtXDiscontinuity)
     }
 }
diff --git a/src/tags/media_segment/map.rs b/src/tags/media_segment/map.rs
index c5c9933..1ef468b 100644
--- a/src/tags/media_segment/map.rs
+++ b/src/tags/media_segment/map.rs
@@ -100,13 +100,7 @@ mod test {
         assert_eq!(tag.to_string(), text);
         assert_eq!(tag.requires_version(), ProtocolVersion::V6);
 
-        let tag = ExtXMap::with_range(
-            "foo",
-            ByteRange {
-                length: 9,
-                start: Some(2),
-            },
-        );
+        let tag = ExtXMap::with_range("foo", ByteRange::new(9, Some(2)));
         let text = r#"#EXT-X-MAP:URI="foo",BYTERANGE="9@2""#;
         track_try_unwrap!(ExtXMap::from_str(text));
         assert_eq!(text.parse().ok(), Some(tag.clone()));
diff --git a/src/types/byte_range.rs b/src/types/byte_range.rs
index af26870..443ab53 100644
--- a/src/types/byte_range.rs
+++ b/src/types/byte_range.rs
@@ -1,18 +1,32 @@
-use crate::{Error, ErrorKind, Result};
 use std::fmt;
 use std::str::{self, FromStr};
+
+use getset::{Getters, MutGetters, Setters};
 use trackable::error::ErrorKindExt;
 
+use crate::{Error, ErrorKind, Result};
+
 /// Byte range.
 ///
 /// See: [4.3.2.2. EXT-X-BYTERANGE]
 ///
 /// [4.3.2.2. EXT-X-BYTERANGE]: https://tools.ietf.org/html/rfc8216#section-4.3.2.2
-#[allow(missing_docs)]
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[derive(Getters, Setters, MutGetters, Debug, Clone, Copy, PartialEq, Eq, Hash)]
+#[get = "pub"]
+#[set = "pub"]
+#[get_mut = "pub"]
 pub struct ByteRange {
-    pub length: usize,
-    pub start: Option<usize>,
+    /// The length of the range.
+    length: usize,
+    /// The start of the range.
+    start: Option<usize>,
+}
+
+impl ByteRange {
+    /// Creates a new [ByteRange].
+    pub const fn new(length: usize, start: Option<usize>) -> Self {
+        Self { length, start }
+    }
 }
 
 impl fmt::Display for ByteRange {
@@ -27,20 +41,28 @@ impl fmt::Display for ByteRange {
 
 impl FromStr for ByteRange {
     type Err = Error;
+
     fn from_str(s: &str) -> Result<Self> {
-        let mut tokens = s.splitn(2, '@');
-        let length = tokens.next().expect("Never fails");
-        let start = if let Some(start) = tokens.next() {
-            Some(track!(start
-                .parse()
-                .map_err(|e| ErrorKind::InvalidInput.cause(e)))?)
-        } else {
-            None
+        let tokens = s.splitn(2, '@').collect::<Vec<_>>();
+        if tokens.is_empty() {
+            Err(ErrorKind::InvalidInput)?;
+        }
+
+        let length = tokens[0]
+            .parse()
+            .map_err(|e| ErrorKind::InvalidInput.cause(e))?;
+        let start = {
+            let mut result = None;
+            if tokens.len() == 2 {
+                result = Some(
+                    tokens[1]
+                        .parse()
+                        .map_err(|e| ErrorKind::InvalidInput.cause(e))?,
+                );
+            }
+            result
         };
-        Ok(ByteRange {
-            length: track!(length.parse().map_err(|e| ErrorKind::InvalidInput.cause(e)))?,
-            start,
-        })
+        Ok(ByteRange::new(length, start))
     }
 }
 
diff --git a/src/utils.rs b/src/utils.rs
index 605eb1d..946dab9 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -44,6 +44,19 @@ pub(crate) fn quote<T: ToString>(value: T) -> String {
     format!("\"{}\"", value.to_string().replace("\"", ""))
 }
 
+/// Checks, if the given tag is at the start of the input. If this is the case, it will remove it
+/// return the rest of the input, otherwise it will return an error.
+pub(crate) fn tag<T>(input: &str, tag: T) -> crate::Result<&str>
+where
+    T: AsRef<str>,
+{
+    if !input.starts_with(tag.as_ref()) {
+        Err(ErrorKind::InvalidInput)?; // TODO!
+    }
+    let result = input.split_at(tag.as_ref().len()).1;
+    Ok(result)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -74,4 +87,21 @@ mod tests {
         assert_eq!(quote("value"), "\"value\"".to_string());
         assert_eq!(quote("\"value\""), "\"value\"".to_string());
     }
+
+    #[test]
+    fn test_tag() {
+        let input = "HelloMyFriendThisIsASampleString";
+
+        let input = tag(input, "Hello").unwrap();
+        assert_eq!(input, "MyFriendThisIsASampleString");
+
+        let input = tag(input, "My").unwrap();
+        assert_eq!(input, "FriendThisIsASampleString");
+
+        let input = tag(input, "FriendThisIs").unwrap();
+        assert_eq!(input, "ASampleString");
+
+        let input = tag(input, "A").unwrap();
+        assert_eq!(input, "SampleString");
+    }
 }