examples/avi-to-ppm: rename to dump-frames

The old name isn't fitting since the program isn't specific to AVI at all...

examples/dump-frames.rs

@@ -0,0 +1,65 @@
+extern crate ffmpeg_next as ffmpeg;
+
+use ffmpeg::format::{input, Pixel};
+use ffmpeg::media::Type;
+use ffmpeg::software::scaling::{context::Context, flag::Flags};
+use ffmpeg::util::frame::video::Video;
+use std::env;
+use std::fs::File;
+use std::io::prelude::*;
+
+fn main() -> Result<(), ffmpeg::Error> {
+    ffmpeg::init().unwrap();
+
+    if let Ok(mut ictx) = input(&env::args().nth(1).expect("Cannot open file.")) {
+        let input = ictx
+            .streams()
+            .best(Type::Video)
+            .ok_or_else(|| ffmpeg::Error::StreamNotFound)?;
+        let video_stream_index = input.index();
+
+        let mut decoder = input.codec().decoder().video()?;
+
+        let mut scaler = Context::get(
+            decoder.format(),
+            decoder.width(),
+            decoder.height(),
+            Pixel::RGB24,
+            decoder.width(),
+            decoder.height(),
+            Flags::BILINEAR,
+        )?;
+
+        let mut frame_index = 0;
+
+        let mut receive_and_process_decoded_frames =
+            |decoder: &mut ffmpeg::decoder::Video| -> Result<(), ffmpeg::Error> {
+                let mut decoded = Video::empty();
+                while decoder.receive_frame(&mut decoded).is_ok() {
+                    let mut rgb_frame = Video::empty();
+                    scaler.run(&decoded, &mut rgb_frame)?;
+                    save_file(&rgb_frame, frame_index).unwrap();
+                    frame_index += 1;
+                }
+                Ok(())
+            };
+
+        for (stream, packet) in ictx.packets() {
+            if stream.index() == video_stream_index {
+                decoder.send_packet(&packet)?;
+                receive_and_process_decoded_frames(&mut decoder)?;
+            }
+        }
+        decoder.send_eof()?;
+        receive_and_process_decoded_frames(&mut decoder)?;
+    }
+
+    Ok(())
+}
+
+fn save_file(frame: &Video, index: usize) -> std::result::Result<(), std::io::Error> {
+    let mut file = File::create(format!("frame{}.ppm", index))?;
+    file.write_all(format!("P6\n{} {}\n255\n", frame.width(), frame.height()).as_bytes())?;
+    file.write_all(frame.data(0))?;
+    Ok(())
+}