Refactor crate::codec (shssoichiro#78)

* Refactor AVCodec wrapper

* Implement new config interface

* Move ProfileIter to codec::profile

* Add CodecDescriptor

Author: FreezyLemon

examples/codec-info.rs

@@ -20,7 +20,7 @@ fn main() {
                 println!("\t profiles: none");
             }
 
-            if let Ok(video) = codec.video() {
+            if let Some(video) = codec.video() {
                 if let Some(rates) = video.rates() {
                     println!("\t rates: {:?}", rates.collect::<Vec<_>>());
                 } else {
@@ -34,7 +34,7 @@ fn main() {
                 }
             }
 
-            if let Ok(audio) = codec.audio() {
+            if let Some(audio) = codec.audio() {
                 if let Some(rates) = audio.rates() {
                     println!("\t rates: {:?}", rates.collect::<Vec<_>>());
                 } else {
@@ -71,7 +71,7 @@ fn main() {
                 println!("\t profiles: {:?}", profiles.collect::<Vec<_>>());
             }
 
-            if let Ok(video) = codec.video() {
+            if let Some(video) = codec.video() {
                 if let Some(rates) = video.rates() {
                     println!("\t rates: {:?}", rates.collect::<Vec<_>>());
                 } else {
@@ -85,7 +85,7 @@ fn main() {
                 }
             }
 
-            if let Ok(audio) = codec.audio() {
+            if let Some(audio) = codec.audio() {
                 if let Some(rates) = audio.rates() {
                     println!("\t rates: {:?}", rates.collect::<Vec<_>>());
                 } else {

examples/transcode-audio.rs

@@ -83,7 +83,8 @@ fn transcoder<P: AsRef<Path>>(
     let mut decoder = context.decoder().audio()?;
     let codec = ffmpeg::encoder::find(octx.format().codec(path, media::Type::Audio))
         .expect("failed to find encoder")
-        .audio()?;
+        .audio()
+        .expect("encoder is not audio encoder");
     let global = octx
         .format()
         .flags()