util/frame/audio: rename new to empty and make new allocate the buffers

src/util/frame/audio.rs

@@ -9,10 +9,24 @@ use super::Frame;
 pub struct Audio(Frame);
 
 impl Audio {
-	pub fn new() -> Self {
+	pub fn empty() -> Self {
 		Audio(Frame::new())
 	}
 
+	pub fn new(format: format::Sample, samples: usize, layout: i64) -> Self {
+		unsafe {
+			let mut frame = Audio(Frame::new());
+
+			frame.set_format(format);
+			frame.set_samples(samples);
+			frame.set_channel_layout(layout);
+
+			av_frame_get_buffer(frame.ptr, 1);
+
+			frame
+		}
+	}
+
 	pub fn format(&self) -> format::Sample {
 		unsafe {
 			if (*self.ptr).format == -1 {
@@ -24,6 +38,12 @@ impl Audio {
 		}
 	}
 
+	pub fn set_format(&mut self, value: format::Sample) {
+		unsafe {
+			(*self.ptr).format = mem::transmute::<AVSampleFormat, c_int>(value.into());
+		}
+	}
+
 	pub fn channel_layout(&self) -> i64 {
 		unsafe {
 			av_frame_get_channel_layout(self.ptr)