Demuxer: emit an error in case of unknown data packets and EOF (#32)

At the moment, the demuxer returns (nil, nil) when the stream
is finished, there are TS packets in the queue but they're
unknown data packets.

This patch makes the demuxer emit (nil, ErrNoMorePackets).

demuxer.go

@@ -119,14 +119,16 @@ func (dmx *Demuxer) NextData() (d *DemuxerData, err error) {
 					}
 
 					// Parse data
-					if ds, err = parseData(ps, dmx.optPacketsParser, dmx.programMap); err != nil {
+					var errParseData error
+					if ds, errParseData = parseData(ps, dmx.optPacketsParser, dmx.programMap); errParseData != nil {
 						// We need to silence this error as there may be some incomplete data here
 						// We still want to try to parse all packets, in case final data is complete
 						continue
 					}
 
 					// Update data
 					if d = dmx.updateData(ds); d != nil {
+						err = nil
 						return
 					}
 				}

demuxer_test.go

@@ -101,6 +101,27 @@ func TestDemuxerNextData(t *testing.T) {
 	assert.EqualError(t, err, ErrNoMorePackets.Error())
 }
 
+func TestDemuxerNextDataUnknownDataPackets(t *testing.T) {
+	buf := &bytes.Buffer{}
+	bufWriter := astikit.NewBitsWriter(astikit.BitsWriterOptions{Writer: buf})
+
+	// Packet that isn't a data packet (PSI or PES)
+	b1, _ := packet(PacketHeader{
+		ContinuityCounter:         uint8(0),
+		PID:                       256,
+		PayloadUnitStartIndicator: true,
+		HasPayload:                true,
+	}, PacketAdaptationField{}, []byte{0x01, 0x02, 0x03, 0x04}, true)
+	bufWriter.Write(b1)
+
+	// The demuxer must return "no more packets"
+	dmx := NewDemuxer(context.Background(), bytes.NewReader(buf.Bytes()),
+		DemuxerOptPacketSize(188))
+	d, err := dmx.NextData()
+	assert.Equal(t, (*DemuxerData)(nil), d)
+	assert.EqualError(t, err, ErrNoMorePackets.Error())
+}
+
 func TestDemuxerNextDataPATPMT(t *testing.T) {
 	pat := hexToBytes(`474000100000b00d0001c100000001f0002ab104b2ffffffffffffffff
 	ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff