Hi,
I am having a problem with the video / audio sync when recording from an RTSP
stream with ffmpeg.
This is the script I am using (only doing a 10 second clip for test):
-channel_layout mono -i "rtsp://172.16.210.50/RTP-Unicast_pMediaProfile4" -c:v
copy -bsf:a aac_adtstoasc -y
-t 10 -movflags faststart "streamtest_high_%datetimef%.mp4"
Which seems to capture the source without any errors:
C:\STREAMTEST>c:\ffmpeg\ffmpeg -channel_layout mono -i "rtsp://172.16.210.50/RTP
-Unicast_pMediaProfile4" -c:v copy -bsf:a aac_adtstoasc -y -t 10 -movflags fasts
tart "streamtest_high_30012015_102911.mp4"
ffmpeg version N-69406-ga73c411 Copyright (c) 2000-2015 the FFmpeg developers
built on Jan 29 2015 22:02:28 with gcc 4.9.2 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
le-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --
enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-lib
modplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrw
b --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinge
r --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --en
able-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis
--enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-
libx265 --enable-libxavs --enable-libxvid --enable-lzma --enable-decklink --enab
le-zlib
libavutil 54. 18.100 / 54. 18.100
libavcodec 56. 21.101 / 56. 21.101
libavformat 56. 19.100 / 56. 19.100
libavdevice 56. 4.100 / 56. 4.100
libavfilter 5. 9.101 / 5. 9.101
libswscale 3. 1.101 / 3. 1.101
libswresample 1. 1.100 / 1. 1.100
libpostproc 53. 3.100 / 53. 3.100
Input #0, rtsp, from 'rtsp://172.16.210.50/RTP-Unicast_pMediaProfile4':
Metadata:
title : Session streamed by Oslo
comment : RTP-Unicast_pMediaProfile4
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
Stream #0:1: Video: h264 (Baseline), yuv420p, 1280x720, 25 fps, 25 tbr, 90k
tbn, 50 tbc
Output #0, mp4, to 'streamtest_high_30012015_102911.mp4':
Metadata:
title : Session streamed by Oslo
comment : RTP-Unicast_pMediaProfile4
encoder : Lavf56.19.100
Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 1280x720, q=2-31
, 25 fps, 25 tbr, 90k tbn, 90k tbc
Stream #0:1: Audio: aac (libvo_aacenc) ([64][0][0][0] / 0x0040), 8000 Hz, mo
no, s16, 128 kb/s
Metadata:
encoder : Lavc56.21.101 libvo_aacenc
Stream mapping:
Stream #0:1 -> #0:0 (copy)
Stream #0:0 -> #0:1 (pcm_mulaw (native) -> aac (libvo_aacenc))
Press [q] to stop, [?] for help
frame= 43 fps=0.0 q=-1.0 size= 566kB time=00:00:02.58 bitrate=1795.0kbits/
frame= 56 fps= 53 q=-1.0 size= 863kB time=00:00:03.10 bitrate=2277.3kbits/
frame= 68 fps= 43 q=-1.0 size= 1138kB time=00:00:03.59 bitrate=2596.3kbits/
frame= 81 fps= 39 q=-1.0 size= 1403kB time=00:00:04.10 bitrate=2803.0kbits/
frame= 95 fps= 36 q=-1.0 size= 1646kB time=00:00:04.66 bitrate=2893.5kbits/
frame= 108 fps= 34 q=-1.0 size= 1900kB time=00:00:05.18 bitrate=3001.6kbits/
frame= 120 fps= 33 q=-1.0 size= 2159kB time=00:00:05.66 bitrate=3122.7kbits/
frame= 134 fps= 32 q=-1.0 size= 2325kB time=00:00:06.22 bitrate=3060.6kbits/
frame= 147 fps= 31 q=-1.0 size= 2583kB time=00:00:06.73 bitrate=3139.3kbits/
frame= 159 fps= 31 q=-1.0 size= 2829kB time=00:00:07.21 bitrate=3210.4kbits/
frame= 172 fps= 30 q=-1.0 size= 3163kB time=00:00:07.74 bitrate=3346.2kbits/
frame= 186 fps= 30 q=-1.0 size= 3378kB time=00:00:08.30 bitrate=3332.5kbits/
frame= 199 fps= 29 q=-1.0 size= 3598kB time=00:00:08.82 bitrate=3341.1kbits/
frame= 211 fps= 29 q=-1.0 size= 3902kB time=00:00:09.30 bitrate=3436.8kbits/
frame= 224 fps= 29 q=-1.0 size= 4181kB time=00:00:09.81 bitrate=3489.1kbits/
[mp4 @ 04dfb960] Starting second pass: moving the moov atom to the beginning of
the file
frame= 228 fps= 28 q=-1.0 Lsize= 4402kB time=00:00:10.05 bitrate=3587.7kbits
/s
video:4382kB audio:13kB subtitle:0kB other streams:0kB global headers:0kB muxing
overhead: 0.138498%
The result seems leave the video and audio out of sync in Windows Media Player
(which unfortunately is the application I need to use for this), where as VLC
seems to be able to cope with this and rectifies the problem.
I thought that it maybe a buffering problem, that ffmpeg is writing the audio
track as soon as it receives it, which must be before the video track. I had
some success with the -ss command by delaying the recording by x seconds, which
seemed to work on some systems but not others.
Does anyone have any idea what is causing this, and provide any suggestions?
Many thanks in advance
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