diff --git a/examples/main.rs b/examples/main.rs
index a8a5cad..0b7cb8f 100644
--- a/examples/main.rs
+++ b/examples/main.rs
@@ -6,7 +6,6 @@ fn main() -> anyhow::Result<()> {
     let mut arg = env::args();
     arg.next(); // skip executable
     let filename = arg.next().ok_or(anyhow::anyhow!("unexpected"))?;
-    let frames = arg.next().unwrap_or("frames".into());
-    decode_to_files(&filename, &frames)?;
+    decode_to_files(&filename)?;
     Ok(())
 }
diff --git a/src/lib.rs b/src/lib.rs
index 4731b9a..f3ea571 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -251,15 +251,26 @@ fn decode(filename: &str) -> PyResult<PyFrameIterator> {
     Ok(iter.into())
 }
 
-pub fn decode_to_files(filename: &str, frames_root: &str) -> anyhow::Result<()> {
+/// writes to frames/<basename of filename>
+pub fn decode_to_files(filename: &str) -> anyhow::Result<()> {
     let frameiter = Decoder::new(filename)?;
+    let basename = std::path::Path::new(filename)
+        .file_stem()
+        .ok_or(anyhow::anyhow!("cannot get basename"))?
+        .to_str()
+        .ok_or(anyhow::anyhow!("cannot convert to utf-8 from os name"))?;
+    let target_dir = format!("frames/{}", basename);
+    let target_dir = std::path::Path::new(&target_dir);
+    if !target_dir.exists() {
+        std::fs::create_dir(target_dir)?;
+    }
     for (i, frame) in frameiter.enumerate() {
-        let name = format!("{}/{:05}.png", frames_root, i);
+        let name = format!("frames/{}/{:05}.png", basename, i);
         if let Err(_e) = write_raw_frame(&name, &frame.raw) {
             println!("skipping bad frame {}", i);
             continue;
         }
-        let name = format!("{}/temp_{:05}.png", frames_root, i);
+        let name = format!("{}/temp_{:05}.png", target_dir.display(), i);
         let pixels = frame.pixels();
         write_calibrated_frame(&name, &pixels)?;
     }
diff --git a/thermal.mp4 b/thermal.mp4
index 4665d9b..cd76de9 100644
Binary files a/thermal.mp4 and b/thermal.mp4 differ