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cleanup resent data code in raop_rtp.c

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This commit is contained in:
fduncanh
2022-06-11 14:28:30 -04:00
parent 42f37f15b4
commit 64a7dd0fa0
1 changed files with 40 additions and 24 deletions
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64
lib/raop_rtp.c
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@@ -425,9 +425,8 @@ raop_rtp_thread_udp(void *arg)
struct sockaddr_storage saddr;
socklen_t saddrlen;
bool have_synced = false;
bool audio_stream_started = false;
bool audio_data_started = false;
unsigned char empty_packet_marker[] = {0x00, 0x34, 0x68, 0x00};
const int resend_offset = 4;
/* the 44.1 kHZ rtp_time epoch is about 27 hours */
bool have_rtp_time = false;
int64_t rtp_time; /* will only change by small amounts to track rtp epoch changes */
@@ -479,12 +478,15 @@ raop_rtp_thread_udp(void *arg)
raop_rtp->control_saddr_len = saddrlen;
int type_c = packet[1] & ~0x80;
logger_log(raop_rtp->logger, LOGGER_DEBUG, "\nraop_rtp type_c 0x%02x, packetlen = %d", type_c, packetlen);
if (type_c == 0x56 && packetlen >= resend_offset + 4) {
/* Handle resent data packet */
unsigned short seqnum = byteutils_get_short_be(packet, resend_offset + 2);
if (packetlen > resend_offset + 12) {
logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp audio resent: seqnum=%u", seqnum);
int result = raop_buffer_enqueue(raop_rtp->buffer, packet + resend_offset, packetlen - resend_offset, 1);
if (type_c == 0x56 && packetlen >= 8) {
/* Handle resent data packet, which begins at offset 4 of these packets */
unsigned char *resent_packet = &packet[4];
unsigned int resent_packetlen = packetlen - 4;
unsigned short seqnum = byteutils_get_short_be(resent_packet, 2);
if (resent_packetlen > 12) {
logger_log(raop_rtp->logger, LOGGER_DEBUG, "raop_rtp audio resent packet: seqnum=%u", seqnum);
int result = raop_buffer_enqueue(raop_rtp->buffer, resent_packet, resent_packetlen, 1);
assert(result >= 0);
} else {
/* type_c = 0x56 packets with length 8 have been reported */
@@ -532,23 +534,37 @@ raop_rtp_thread_udp(void *arg)
}
}
/* rtp un-resent audio data packets: *
* packet[0] 0x80 (both AAC-ELD and ALAC) *
* packet[1] 0x60 = 96 *
* packet[2:3] seqnum (big-endian unsigned short) *
* packet[4:7] rtp timestamp (big-endian unsigned int) *
* packet[8:11] 0x00 0x00 0x00 0x00 *
* packet[12:packetlen - 1] encrypted audio payload */
/* consecutive AAC-ELD rtp timestamps differ by spf = 480 *
* consecutive ALAC rtp timestamps differ by spf = 352 *
* both have PCM uncompressed sampling rate = 441000 Hz */
/* rtp audio data packets:
* packet[0] 0x80
* packet[1] 0x60 = 96
* packet[2:3] seqnum (big-endian unsigned short)
* packet[4:7] rtp timestamp (big-endian unsigned int)
* packet[8:11] 0x00 0x00 0x00 0x00
* packet[12:packetlen - 1] encrypted audio payload
* For (AAC-ELD only), the payload of initial packets at the start of
* the stream may be replaced by a 4-byte "no_data_marker" 0x00 0x68 0x34 0x00 */
/* consecutive AAC-ELD rtp timestamps differ by spf = 480
* consecutive ALAC rtp timestamps differ by spf = 352
* both have PCM uncompressed sampling rate = 441000 Hz */
/* clock time in microseconds advances at (rtp_timestamp * 1000000)/44100 between frames */
/* every AAC-ELD packet is sent three times: 0 0 1 0 1 2 1 2 3 2 3 4 ... *
* (after decoding AAC-ELD into PCM, the sound frame is three times bigger) *
* ALAC packets are sent once only 0 1 2 3 4 5 ... */
/* every AAC-ELD packet is sent three times: 0 0 1 0 1 2 1 2 3 2 3 4 ...
* (after decoding AAC-ELD into PCM, the sound frame is three times bigger)
* ALAC packets are sent once only 0 1 2 3 4 5 ... */
/* When the AAC-ELD audio stream starts, the initial packets are length-16 packets with
* a four-byte "no_data_marker" 0x00 0x68 0x34 0x00 replacing the payload.
* The 12-byte packetheader contains a secnum and rtp_timestamp, and each packets is sent
* three times; the secnum and rtp_timestamp increment according to the same pattern as
* AAC-ELD packets with audio content.*/
/* When the ALAC audio stream starts, the initial packets are length-44 packets with
* the same 32-byte encrypted payload which after decryption is the beginning of a
* 32-byte ALAC packet, presumably with format information, but not actual audio data.
* The secnum and rtp_timestamp in the packet header increment according to the same
* pattern as ALAC packets with audio content */
if (FD_ISSET(raop_rtp->dsock, &rfds)) {
//logger_log(raop_rtp->logger, LOGGER_INFO, "Would have data packet in queue");
@@ -564,8 +580,8 @@ raop_rtp_thread_udp(void *arg)
if (packetlen == 16 && !memcmp(&packet[12], empty_packet_marker, 4)) {
/* skip packet: these marked empty packets occur before first time syncronization */
} else {
if (!audio_stream_started) {
audio_stream_started = true;
if (!audio_data_started) {
audio_data_started = true;
if (have_synced == false) {
/* until the first rtp sync occurs, we don't know the exact client ntp timestamp that matches the client rtp timesamp */
uint32_t rtp_timestamp = byteutils_get_int_be(packet, 4);