streaming

commit 6fdf3f5dfcf476c83866ac084b8609cd5c9db62f
parent f0e60574d2b92126423a85c15191f584bfb1b2e4
Author: Oliver Lowe <o@olowe.co>
Date:   Mon, 10 Jun 2024 13:51:13 +1000

mpegts: correctly pack PCR with reserved bits

The reserved bits needed to be toggled. We've also added our test
which does a byte-for-byte check on packets and reports which bytes
differ after encoding.

Diffstat:
M
mpegts/codec.go
 | 
3
++-
M
mpegts/codec_test.go
 | 
30
+++++++++++++++++++++++++++---

2 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/mpegts/codec.go b/mpegts/codec.go
@@ -251,7 +251,8 @@ func putPCR(b []byte, pcr *PCR) error {
 	b[2] = byte(pcr.Base >> 16)
 	b[3] = byte(pcr.Base >> 24)
 	b[4] = byte(pcr.Base >> 32)
-	// next 6 bits are reserved
+
+	b[4] |= 0x7e // toggle 6 reserved bits
 
 	var emax uint16 = 512 - 1 // max 9-bit int
 	if pcr.Extension > emax {
diff --git a/mpegts/codec_test.go b/mpegts/codec_test.go
@@ -1,6 +1,7 @@
 package mpegts
 
 import (
+	"bytes"
 	"errors"
 	"io"
 	"os"
@@ -13,15 +14,38 @@ func TestDecode(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer f.Close()
+	var i int
 	for {
-		p, err := Decode(f)
+		i++
+		var in [188]byte
+		n, err := f.Read(in[:])
 		if errors.Is(err, io.EOF) {
 			break
+		} else if n != PacketSize {
+			t.Fatalf("short read: read %d bytes", n)
 		} else if err != nil {
+			t.Fatalf("read packet: %v", err)
+		}
+		p, err := Decode(bytes.NewReader(in[:]))
+		if err != nil {
 			t.Fatalf("decode packet: %v", err)
 		}
-		if err := Encode(io.Discard, p); err != nil {
-			t.Fatalf("encode packet: %v", err)
+
+		buf := &bytes.Buffer{}
+		if err := Encode(buf, p); err != nil {
+			t.Fatalf("encode packet %d: %v", i, err)
+		}
+		var out [188]byte
+		copy(out[:], buf.Bytes())
+
+		if in != out {
+			t.Errorf("packet %d: encoded and source bytes differ", i)
+			t.Logf("%+v", p)
+			for i := range in {
+				if in[i] != out[i] {
+					t.Errorf("byte %d: source %v, encoded %v", i, in[i], out[i])
+				}
+			}
 		}
 	}
 }