rtpenc: Don't set max_frames_per_packet based on the packet frame size or frame rate

Instead check the timestamps while muxing, to avoid buffering a
too long timestamp range into one single packet.

This makes the AMR and AAC packetization slightly less efficient,
since we set a possibly unnecessarily high max_frames_per_packet.
(These packetizers end up doing a memmove of the TOC bytes if
sending a packet before max_frames_per_packet is achieved, and
we end up setting max_frames_per_packet to a value that should
be high enough for most uses.)

All packetizers that use max_frames_per_packet now set it either
to a default value, or to a value calculated based on other
parameters, so none of them rely on the previous default setting.

For iLBC, copy one frame at a time, to allow checking the timestamp
range for each of them - basically doing potentially multiple
loops to simplify the code instead of trying to calculate the
number of frames to buffer while honoring s1->max_delay.

This is in preparation for reducing the coupling between libavformat
and libavcodec, by not having the muxers use the encoder field
frame_size (which may not be available during e.g. stream copy).

Signed-off-by: Martin Storsjö <martin@martin.st>

1 files changed, 4 insertions, 1 deletions

diff --git a/libavformat/rtpenc_aac.c b/libavformat/rtpenc_aac.c
index 7805ab9034..d0b4ca0964 100644
--- a/libavformat/rtpenc_aac.c
+++ b/libavformat/rtpenc_aac.c
@@ -27,6 +27,7 @@
 void ff_rtp_send_aac(AVFormatContext *s1, const uint8_t *buff, int size)
 {
     RTPMuxContext *s = s1->priv_data;
+    AVStream *st = s1->streams[0];
     const int max_au_headers_size = 2 + 2 * s->max_frames_per_packet;
     int len, max_packet_size = s->max_payload_size - max_au_headers_size;
     uint8_t *p;
@@ -41,7 +42,9 @@ void ff_rtp_send_aac(AVFormatContext *s1, const uint8_t *buff, int size)
     len = (s->buf_ptr - s->buf);
     if (s->num_frames &&
         (s->num_frames == s->max_frames_per_packet ||
-         (len + size) > s->max_payload_size)) {
+         (len + size) > s->max_payload_size ||
+         av_compare_ts(s->cur_timestamp - s->timestamp, st->time_base,
+                       s1->max_delay, AV_TIME_BASE_Q) >= 0)) {
         int au_size = s->num_frames * 2;
 
         p = s->buf + max_au_headers_size - au_size - 2;