commit 702e6ac1e1ab11b1adea9404b0170c28f46681ef
Author: Nathan Vegdahl <cessen@cessen.com>
Date:   Tue Apr 19 14:02:12 2022 -0700

    First code that actually decodes and writes out a frame of video!

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diff --git a/Cargo.toml b/Cargo.toml
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index 0000000..15a35c7
--- /dev/null
+++ b/Cargo.toml
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+[package]
+name = "ffmpeg_rust"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+ffmpeg-next = "5.0.3"
+png = "0.17.5"
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..80d3646
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,104 @@
+use std::fs::File;
+use std::io::BufWriter;
+
+extern crate ffmpeg_next as ffmpeg;
+use ffmpeg::{software::scaling::flag::Flags, util::format::pixel::Pixel};
+
+fn main() {
+    let input_path = std::env::args().nth(1).expect("missing input file");
+    let output_path = std::env::args().nth(2).expect("missing ouput file");
+
+    ffmpeg::init().unwrap();
+    ffmpeg::log::set_level(ffmpeg::log::Level::Info);
+
+    // Open the file and dump some info about it to the console.
+    let mut input_ctx = ffmpeg::format::input(&input_path).unwrap();
+    ffmpeg::format::context::input::dump(&input_ctx, 0, Some(&input_path));
+
+    // Get the "best" video stream.
+    // (It's not clear to me what that means, but I'm going with it.)
+    let stream = input_ctx
+        .streams()
+        .best(ffmpeg::media::Type::Video)
+        .unwrap();
+    let stream_idx = stream.index() as usize;
+
+    // Create a decoder for the video stream.
+    let mut decoder = ffmpeg::codec::context::Context::from_parameters(stream.parameters())
+        .unwrap()
+        .decoder()
+        .video()
+        .unwrap();
+
+    // Create a converter to get the video frames into the color format
+    // we want.
+    // It's a bit weird, but we do this by creating a scaler, which also
+    // resizes images.  Apparently it's an all-in-one kind of thing for
+    // scaling and color format conversion.
+    let mut converter = ffmpeg::software::scaling::context::Context::get(
+        decoder.format(),
+        decoder.width(),
+        decoder.height(),
+        Pixel::RGB24, // Output color format.
+        decoder.width(),
+        decoder.height(),
+        Flags::POINT, // Nearest neighbor, since we're not actually scaling.
+    )
+    .unwrap();
+
+    // Place to store the image data.
+    let mut width = 0;
+    let mut height = 0;
+    let mut pixels = Vec::new();
+
+    // Get the first frame of the video.
+    // To access it we have to process packets until the frame is
+    // available.
+    let mut decoded_frame = ffmpeg::util::frame::video::Video::empty();
+    for (stream, packet) in input_ctx.packets() {
+        if stream.index() == stream_idx {
+            decoder.send_packet(&packet).unwrap();
+            if decoder.receive_frame(&mut decoded_frame).is_ok() {
+                // Convert to RGB.
+                let mut converted_frame = ffmpeg::util::frame::video::Video::empty();
+                converter.run(&decoded_frame, &mut converted_frame).unwrap();
+
+                // Save the image data to our own in-memory area.
+                width = converted_frame.width() as u32;
+                height = converted_frame.height() as u32;
+                // The `0` parameter is the plane.  For this pixel format
+                // there's just one plane anyway.
+                for byte in converted_frame.data(0).iter() {
+                    pixels.push(*byte);
+                }
+
+                // We got the first frame, so stop.
+                break;
+            }
+        }
+    }
+
+    // Write out a PNG file.
+    let mut encoder = png::Encoder::new(
+        BufWriter::new(File::create(output_path).unwrap()),
+        width,
+        height,
+    );
+    encoder.set_color(png::ColorType::Rgb);
+    encoder.set_depth(png::BitDepth::Eight);
+    let mut writer = encoder.write_header().unwrap();
+    writer.write_image_data(&pixels).unwrap();
+
+    println!("{:?}", decoder.format());
+}
+
+// Returns the number of bits needed to store any of the pixel channels
+// for a given format.
+fn pixel_channel_size(f: Pixel) -> usize {
+    use Pixel::*;
+    match f {
+        YUV420P => 8,
+        YUV422P10LE => 10,
+        _ => panic!("Haven't decided how to decode '{:?}' yet", f),
+    }
+}