Generated sdp file missing audio

[gardinal]

Summary of the bug:
The sdp file generated is different than the console output, and is missing m=audio.
How to reproduce:

% ffmpeg -rtsp_transport tcp -i rtsp://user:pass@10.0.0.27 -vcodec copy -an -f rtp rtp://127.0.0.1:11110 -vn -acodec copy -f rtp rtp://127.0.0.1:11112 -sdp_file ./input.sdp
ffmpeg version 6.1

Console output:

Input #0, rtsp, from 'rtsp://admin:bsts1111@10.0.0.27':
  Metadata:
    title           : h264.mp4
  Duration: N/A, start: 0.000000, bitrate: N/A
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 2592x1944, 30 fps, 60 tbr, 90k tbn
  Stream #0:1: Audio: aac (LC), 48000 Hz, mono, fltp
Output #0, rtp, to 'rtp://127.0.0.1:11110':
  Metadata:
    title           : h264.mp4
    encoder         : Lavf60.16.100
  Stream #0:0: Video: h264 (High), yuv420p(progressive), 2592x1944, q=2-31, 30 fps, 60 tbr, 90k tbn
Output #1, rtp, to 'rtp://127.0.0.1:11112':
  Metadata:
    title           : h264.mp4
    encoder         : Lavf60.16.100
  Stream #1:0: Audio: aac (LC), 48000 Hz, mono, fltp
SDP:
v=0
o=- 0 0 IN IP4 127.0.0.1
s=h264.mp4
t=0 0
a=tool:libavformat 60.16.100
m=video 11110 RTP/AVP 96
c=IN IP4 127.0.0.1
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-sets=Z2TAMqwbGqAogPX5YQAAAwABAAADADyPCIRq,aO4xshsA; profile-level-id=64C032
m=audio 11112 RTP/AVP 97
c=IN IP4 127.0.0.1
a=rtpmap:97 MPEG4-GENERIC/48000/1
a=fmtp:97 profile-level-id=1;mode=AAC-hbr;sizelength=13;indexlength=3;indexdeltalength=3; config=1188

Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #1:0 (copy)

SDP file:

v=0
o=- 0 0 IN IP4 127.0.0.1
s=h264.mp4
c=IN IP4 127.0.0.1
t=0 0
a=tool:libavformat 60.16.100
m=video 11110 RTP/AVP 96
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-sets=Z2TAMqwbGqAogPX5YQAAAwABAAADADyPCIRq,aO4xshsA; profile-level-id=64C032