Initialize gstreamer only once

.gitignore

@@ -1,2 +1,3 @@
 /target
 Cargo.lock
+*.png

examples/simple.rs

@@ -0,0 +1,18 @@
+use std::path::Path;
+use std::fs::File;
+use std::io::Write;
+
+// Capture fist frame of the video file
+fn main() {
+    let file_path = Path::new("resources/video.mp4");
+    let mut first_frame = File::create("first_frame.png").unwrap();
+
+    let frame_source = vid2img::FileSource::new(file_path, (1280, 534)).unwrap();
+    for frame in frame_source.into_iter() {
+        if let Ok(Some(png_img_data)) = frame {
+            println!("{}", png_img_data.len());
+            first_frame.write_all(&png_img_data).unwrap();
+            break;
+        }
+    }
+}

src/file.rs

@@ -1,6 +1,8 @@
 use crate::StreamError;
 use crate::{FrameData, VideoStream, VideoStreamIterator};
 use std::path::{Path, PathBuf};
+use std::fs;
+use std::io;
 
 pub struct FileSource {
     source: PathBuf,
@@ -9,11 +11,12 @@ pub struct FileSource {
 
 impl FileSource {
     pub fn new(source: &Path, frame_size: (u32, u32)) -> Result<Self, CaptureError> {
+        let source = fs::canonicalize(source)?;
         if !source.exists() {
             return Err(CaptureError::FileNotFound);
         }
         Ok(Self {
-            source: source.to_path_buf(),
+            source,
             frame_size,
         })
     }
@@ -34,6 +37,14 @@ impl IntoIterator for FileSource {
     }
 }
 
+#[derive(Debug)]
 pub enum CaptureError {
+    IoError(io::Error),
     FileNotFound,
 }
+
+impl From<io::Error> for CaptureError {
+    fn from(err: io::Error) -> Self {
+        CaptureError::IoError(err)
+    }
+}

src/lib.rs

@@ -14,12 +14,11 @@
 //!
 //! ```no_run
 //! use std::path::Path;
-//! use vid2img::FileSource;
 //!
 //! fn main() {
 //!     let file_path = Path::new("video.mp4");
 //!
-//!     let frame_source = FileSource::new(file_path, (200, 200)).unwrap();
+//!     let frame_source = vid2img::FileSource::new(file_path, (200, 200)).unwrap();
 //!     for frame in frame_source.into_iter() {
 //!         if let Ok(Some(png_img_data)) = frame {
 //!             // do something with the image data here ...

src/video_stream.rs

@@ -3,21 +3,29 @@ use gst::prelude::*;
 use gstreamer as gst;
 use gstreamer_app as gst_app;
 use std::sync::mpsc::{sync_channel, Receiver, TryRecvError, TrySendError};
+use std::sync::Once;
 
 pub type FrameData = Vec<u8>;
 
+static INIT_GST: Once = Once::new();
+
 pub struct VideoStream {
     pipeline_description: String,
 }
 
 impl VideoStream {
     pub fn new<S: AsRef<str>>(pipeline_description: S) -> Self {
+        INIT_GST.call_once(|| {
+            log::trace!("Initializing GStreamer..");
+            gst::init().expect("Could not initialize GStreamer!");
+        });
         Self {
             pipeline_description: String::from(pipeline_description.as_ref()),
         }
     }
 }
 
+#[derive(Debug)]
 pub struct GstErrorMessage {
     pub src: String,
     pub error: String,
@@ -25,6 +33,7 @@ pub struct GstErrorMessage {
     pub source: glib::Error,
 }
 
+#[derive(Debug)]
 pub enum StreamError {
     GstError(GstErrorMessage),
     FrameCaptureError,