container/mts: wrote function BytesForMetaInterval to return media between two points of meta.

container/mts/payload.go

@@ -8,7 +8,8 @@ import (
 	"github.com/Comcast/gots/pes"
 )
 
-// Extract extracts the media from an MPEG-TS clip given by p.
+// Extract extracts the media, PTS, stream ID and meta for an MPEG-TS clip given
+// by p, and returns as a Clip. The MPEG-TS must contain only complete packets.
 func Extract(p []byte) (*Clip, error) {
 	l := len(p)
 	// Check that clip is divisible by 188, i.e. contains a series of full MPEG-TS clips.
@@ -121,9 +122,9 @@ func (c *Clip) Bytes() []byte {
 
 // Errors used in BytesForPTSInterval.
 var (
-	errBadLowerBound   = errors.New("'from' cannot be found")
-	errBadUpperBound   = errors.New("'to' cannot be found")
-	errInvalidPTSRange = errors.New("PTS interval invalid")
+	errPTSLowerBound = errors.New("PTS 'from' cannot be found")
+	errPTSUpperBound = errors.New("PTS 'to' cannot be found")
+	errPTSRange      = errors.New("PTS interval invalid")
 )
 
 // BytesForPTSInterval returns the media data between PTS' from and to. If from
@@ -133,7 +134,7 @@ var (
 func (c *Clip) BytesForPTSInterval(from, to uint64) ([]byte, error) {
 	// First check that the interval makes sense.
 	if from >= to {
-		return nil, errInvalidPTSRange
+		return nil, errPTSRange
 	}
 
 	// Use binary search to find 'from'.
@@ -148,7 +149,7 @@ func (c *Clip) BytesForPTSInterval(from, to uint64) ([]byte, error) {
 		},
 	)
 	if idx == n {
-		return nil, errBadLowerBound
+		return nil, errPTSLowerBound
 	}
 
 	// Now get the start index for the backing slice from this Frame.
@@ -167,7 +168,7 @@ func (c *Clip) BytesForPTSInterval(from, to uint64) ([]byte, error) {
 		},
 	)
 	if idx == n {
-		return nil, errBadUpperBound
+		return nil, errPTSUpperBound
 	}
 
 	// Now get the end index for the backing slice from this Frame, and return
@@ -175,3 +176,56 @@ func (c *Clip) BytesForPTSInterval(from, to uint64) ([]byte, error) {
 	end := c.frames[idx+off-1].idx
 	return c.backing[start : end+len(c.frames[idx+off].Media)], nil
 }
+
+// Errors that maybe returned from BytesForMetaInterval.
+var (
+	errMetaRange      = errors.New("invalid meta range")
+	errMetaLowerBound = errors.New("meta 'from' cannot be found")
+	errMetaUpperBound = errors.New("meta 'to' cannot be found")
+)
+
+func (c *Clip) BytesForMetaInterval(key, from, to string) ([]byte, error) {
+	// First check that the interval makes sense.
+	if from >= to {
+		return nil, errMetaRange
+	}
+
+	// Use binary search to find 'from'.
+	n := len(c.frames)
+	idx := sort.Search(
+		n,
+		func(i int) bool {
+			if c.frames[i].Meta[key] == from {
+				return true
+			}
+			return false
+		},
+	)
+	if idx == n {
+		return nil, errMetaLowerBound
+	}
+
+	// Now get the start index for the backing slice from this Frame.
+	start := c.frames[idx].idx
+
+	// Now use binary search again to find 'to'.
+	off := idx + 1
+	n = n - (off)
+	idx = sort.Search(
+		n,
+		func(i int) bool {
+			if c.frames[i+off].Meta[key] == to {
+				return true
+			}
+			return false
+		},
+	)
+	if idx == n {
+		return nil, errMetaUpperBound
+	}
+
+	// Now get the end index for the backing slice from this Frame, and return
+	// segment from backing slice corresponding to start and end.
+	end := c.frames[idx+off].idx
+	return c.backing[start : end+len(c.frames[idx+off].Media)], nil
+}

container/mts/payload_test.go

@@ -280,19 +280,19 @@ func TestBytesForPTSInterval(t *testing.T) {
 			from:   10,
 			to:     5,
 			expect: nil,
-			err:    errInvalidPTSRange,
+			err:    errPTSRange,
 		},
 		{
 			from:   50,
 			to:     70,
 			expect: nil,
-			err:    errBadLowerBound,
+			err:    errPTSLowerBound,
 		},
 		{
 			from:   5,
 			to:     70,
 			expect: nil,
-			err:    errBadUpperBound,
+			err:    errPTSUpperBound,
 		},
 	}