Add more granular error message

pkg/codec/x264/bridge.h

@@ -4,6 +4,12 @@
 #include <stdlib.h>
 #include <x264.h>
 
+#define ERR_DEFAULT_PRESET -1
+#define ERR_APPLY_PROFILE -2
+#define ERR_ALLOC_PICTURE -3
+#define ERR_OPEN_ENGINE -4
+#define ERR_ENCODE -5
+
 typedef struct Slice {
   unsigned char *data;
   int data_len;
@@ -18,8 +24,10 @@ typedef struct Encoder {
 Encoder *enc_new(x264_param_t param) {
   Encoder *e = (Encoder *)malloc(sizeof(Encoder));
 
-  if (x264_param_default_preset(&e->param, "veryfast", "zerolatency") < 0)
+  if (x264_param_default_preset(&e->param, "veryfast", "zerolatency") < 0) {
+    errno = ERR_DEFAULT_PRESET;
     goto fail;
+  }
 
   /* Configure non-default params */
   e->param.i_csp = param.i_csp;
@@ -37,15 +45,21 @@ Encoder *enc_new(x264_param_t param) {
   e->param.b_repeat_headers = 1;
   e->param.b_annexb = 1;
 
-  if (x264_param_apply_profile(&e->param, "baseline") < 0)
+  if (x264_param_apply_profile(&e->param, "baseline") < 0) {
+    errno = ERR_APPLY_PROFILE;
     goto fail;
+  }
 
-  if (x264_picture_alloc(&e->pic_in, param.i_csp, param.i_width, param.i_height) < 0)
+  if (x264_picture_alloc(&e->pic_in, param.i_csp, param.i_width, param.i_height) < 0) {
+    errno = ERR_ALLOC_PICTURE;
     goto fail;
+  }
 
   e->h = x264_encoder_open(&e->param);
-  if (!e->h)
+  if (!e->h) {
+    errno = ERR_OPEN_ENGINE;
     goto fail2;
+  }
 
   return e;
 
@@ -54,8 +68,6 @@ fail2:
 
 fail:
   free(e);
-  // TODO: set appropriate errno
-  errno = -1;
   return NULL;
 }
 
@@ -70,8 +82,7 @@ Slice enc_encode(Encoder *e, uint8_t *y, uint8_t *cb, uint8_t *cr) {
   int frame_size = x264_encoder_encode(e->h, &nal, &i_nal, &e->pic_in, &e->pic_out);
   Slice s = {.data_len = frame_size};
   if (frame_size <= 0) {
-    // TODO: set appropriate errno
-    errno = -1;
+    errno = ERR_ENCODE;
     return s;
   }
 

pkg/codec/x264/x264.go

@@ -10,6 +10,8 @@ import (
 	"fmt"
 	"image"
 	"io"
+	"sync"
+	"syscall"
 	"unsafe"
 
 	"github.com/pion/mediadevices/pkg/codec"
@@ -27,12 +29,32 @@ type encoder struct {
 	closed bool
 }
 
+type cerror int
+
+func (e cerror) Error() string {
+	switch e {
+	case C.ERR_DEFAULT_PRESET:
+		return errDefaultPreset.Error()
+	case C.ERR_APPLY_PROFILE:
+		return errApplyProfile.Error()
+	case C.ERR_ALLOC_PICTURE:
+		return errAllocPicture.Error()
+	case C.ERR_OPEN_ENGINE:
+		return errOpenEngine.Error()
+	case C.ERR_ENCODE:
+		return errEncode.Error()
+	default:
+		return "unknown error"
+	}
+}
+
 var (
-	errInitEngine   = fmt.Errorf("failed to initialize x264")
-	errApplyProfile = fmt.Errorf("failed to apply profile")
-	errAllocPicture = fmt.Errorf("failed to alloc picture")
-	errOpenEngine   = fmt.Errorf("failed to open x264")
-	errEncode       = fmt.Errorf("failed to encode")
+	errInitEngine    = fmt.Errorf("failed to initialize x264")
+	errDefaultPreset = fmt.Errorf("failed to set default preset")
+	errApplyProfile  = fmt.Errorf("failed to apply profile")
+	errAllocPicture  = fmt.Errorf("failed to alloc picture")
+	errOpenEngine    = fmt.Errorf("failed to open x264")
+	errEncode        = fmt.Errorf("failed to encode")
 )
 
 func init() {
@@ -51,7 +73,7 @@ func newEncoder(r video.Reader, p prop.Media) (io.ReadCloser, error) {
 		i_keyint_max: C.int(p.KeyFrameInterval),
 	})
 	if err != nil {
-		return nil, errInitEngine
+		return nil, cerror(err.(syscall.Errno))
 	}
 
 	e := encoder{