WAV I've googled extensively, but still can't seem to find the issue. Starts off in sync and gradually drifts. AntumDeluge. Its not the first choice but a needed option when you have a sync issue. This is wierd for 2 reasons: This ONLY happens with ffmpeg created MP4 and MKV files. We are pushing an rtmp stream to our nginx+ffmpeg transcoder. For this fix, we have to start playing audio earlier. We strech the audio.wav file with the following command and the for a twenty-fifth of a second. On the screenshot above is visible that record.mp4 and If the audio sync makes it unwatchable you wont mind it transcoding. and drop and delete audio.wav. These dv files play perfectly, no audio video sync problems whatsoever. 23 6 6 … Grunt, A slightly confusing part is both problems have a very similar solution that only differs in nuisances. Geeky Hacker wallet number: 1NaGzvbXQtM9PCduXgmFeXe8D4i5C1nDyu. I've tried a variety of settings, including async and vsync, and nothing seems to fix the problem. Sorry, your blog cannot share posts by email. To me this sounds like a ffmpeg exporting problem. I can calculate for both file the amount of 1/25 seconds with the following Enabling "Audio: use only first PTS for sync" makes it out of sync. tracey jaquith archive.org> writes: > I was about to say, "will do", but it turns out I had > been using "-async" properly before, but had various issues > (especially came up with MPEG-TS with 5.1 audio that dropped > down to stereo and lower quality local affiliate commercials for us). The good news is, you can be as granular as milliseconds even. Is this an audio sample issue, where 44100 into 48000 is causing some frame sync problem in the render chain? This seems to work. channel. into a However, audio and video are still not in sync. The origin stream play fine and stays in sync. I could use the NDI monitor to see the video + audio output and although they would start in sync they would gradually drift apart, which was pretty useless! For this fix, we have to start playing audio earlier. When I encode the frames I add the PTS in the following way (which I took from the muxing.c example): For the video frames I increment the PTS one by one (starting at 0). The video starts off fine, but by the end, the audio and video are out of sync by a few seconds! These dv files play perfectly, no audio video sync problems whatsoever. I'm trying to take a ts stream to a mp4 but for some reason the end mp4 is always out of sync. TS to MP4 Audio Sync issues. I'd also be interested in any other options such as the Wolfson audio card. Obviously, but thats the point. - av_strlcatf(args, sizeof(args), ":m ax_soft_comp=%f", audio_sync_method/(double)ist->st->codec->sample_rate); Originally I was using a single command for capture/encode. Note that the only differences are the -map parts. by the amount of s/25 from record.mp4. To put it in simple words, ffmpeg not only allows you to stream audio and … After a lot of fiddling around, I found that the culprit was OBS/this plugin. The only ideas I have are 1) finding the lengths of the two (which is annoying) and delaying the shorter one by the difference between the two lengths, and 2) reversing the two, syncing them, then reversing again. The audio sample rate is 48hz before and after but the puzzling part is that in the case where all I did was extract 25 minutes from the dv file, I didn’t re-encode anything. degree in Computer Science. BAT is a coin that is used by Brave Browser which is getting more popularity day by day. The audio sync problem happens in both places. FFmpeg is the leading multimedia framework, able to decode, encode, transcode, mux, demux, stream, filter and play pretty much anything that humans and machines have created. The video starts off fine, but by the end, the audio and video are out of sync by a few seconds! Something like the following: This file was assembled by mencoder, and I have verified that the audio tones are sent exactly once every 1.001 seconds in the output file. There should be just a muted video channel Prism By using this your container should have little to no audio drift or offset as it will pad the audio with silence or trim audio with negative PTS timestamps if the audio does not actually start at the beginning of the video. VHS Video and audio should have now It is a 24000/1001 (NTSC) MPEG2 sync check file, with every 24th frame showing a coinciding tone and white flash. and audio.wav into Kdenlive via drag and drop. For the simplicity sake, in all the given examples, we pass 3 to -itsoffset. Until sometime last year, audio streams were always the "master" in ffmpeg when it came to synchronization. by Gordon Lesti. When i play a movie after a while the audio starts to be out of sync, and if i pause and unpause the audio gets back in sync, but after a while the same problem occurs. ffmpeg reads the video from /dev/video1, and the audio from tcp://localhost:55555. Drag the record.mp4 source to Video channel and click in In other words, we have to start the video with a delay. With FFmpeg you can do screen casting, podcast recording, cutting files and even mixing audio and video files. I recorded some old In the example, we added three hundred milliseconds delay to the video. I have recorded a 50 minute video, edited it in Hitfilm Express to censor/blur people, and exported it in Hitfilm's high resolution format, generating an 80GB file. Summary of the bug: When I create a MP4 file with AAC Audio or MKV with AC3 Audio the final file, the audio slowly over time drifts out of sync with the video when playing back on a Samsung TV. If you don’t know the exact delay, unfortunately, there’s no easy way rather than trial and error. So far I covered many functionalities of FFmpeg besides the conventional format conversions. $ ffmpeg -i file.mkv -itsoffset 3 -i file.mkv -c:a copy -c:v copy -map 0:a:0 -map 1:v:0 out.mkv. /* maximum audio speed change to get correct sync */ # define SAMPLE_CORRECTION_PERCENT_MAX 10 /* external clock speed adjustment constants for realtime sources based on buffer fullness */ FFmpeg and its photosensitivity filter are not making any medical claims. You can play with some offset flags in ffmpeg, but you kinda have to get lucky and it will eventually drift off anyways. How to combine audio and video using FFmpeg and sync them? You can donate us in Ethereum. now. The resulting file plays fine in VLC but does not in Flash or Quicktime. 2) … Note that this filter is not FDA approved, nor are we medical professionals. Using ffmpeg with the necessary codecs and sound-output is through alsa. Rendering out video + audio via ffmpeg produces audio that doesnt stay in sync. However, when I use ffmpeg -f concat -i mylist.txt -c copy outfile.mp4 to concatenate the title file to the long file, the audio in the long file gradually goes out of sync, progressively becoming worse until at the end of 2 hours, the audio is a full second or two behind the video. Geeky Hacker wallet number: 0x40146D985b995E5bB5b2A7FDc618db689a811DCB. I want to fix this using > ffmpeg without transcoding, just copy.-itsoffset may help: $ ffmpeg -i 1.mp4 -itsoffset 2 -i 1.mp4 -codec copy -map 0:0 -map 1:1 2.mp4 You may have to move the itsoffset (and change between 2 and -2). Here's some of the options I've tried: avconv -i inputvideo.dv -codec copy -ss 00:00:00 -t 1:37:35 output.dv. Is there an easy way to do this with ffmpeg? Hello. Krs Mark It is a 24000/1001 (NTSC) MPEG2 sync check file, with every 24th frame showing a coinciding tone and white flash. **Update: render to libdv seems to work, without this issue of sync drift, only tested on small 15m junk, file is big! video/audio sync drift while doing real time recording with mp4 or mkv while with ffm it's totaly fine ffmpeg -re -f alsa -i default -f x11grab -r 25 -s 1152x864 -i :0.0 -acodec libfaac -vcodec libx264 -preset superfast -threads 1 ~/rec.mkv # or .mp4 With a couple of attempts, you should get a good result. For that, we can use the above command and just tweak a little bit, 1. Hi guys, i am using plex for a long time, and a problem that i always have is an audio drift. Initially (first minute), the audio and video is perfectly in sync. It doesn;t sem to suffer drift its just off from start to finish. Python In the process of digitizing family VHS tapes, amateur video producers often encounter audio drift or skew where the audio track becomes out of sync with the video: It slowly dawned on me that the ... video ffmpeg audio sync. This is wierd for 2 reasons: This ONLY happens with ffmpeg created MP4 and MKV files. 44.1kHz vs 48kHz has nothing to do with the drift. For that, we can use the above command and just tweak a little bit. And The extracted audio should be available as audio.wav file. The ffmpeg command below simply overlays the audio waveform back over the video frames. However, when i try to convert then to ANY format, using ANY video conversion softwares (and i have tried MANY), the resulting video gradually drifts out of sync with the audio. I had this issue a few weeks ago and was disappointed when I found the option had gone after spending 30 minutes over all apps searching for it. The question is if ffmpeg is incorrectly handling the audio when the packets durations are different than video durations, or if the capture code is not handling embedded sources correctly. Detect audio drift. audio bit_rate=64000 sample_rate=44100 channels=2 An odd issue has arisen. The extracted audio should be available as audio.wav file. But the parameter accepts timestamp as granula as milliseconds. This Website is build with Even a fraction of a second makes the video unwatchable, well, for … I can provide the two samples, but each are about 10 seconds long which comes out to 1.1G each. For example. Reply. The ffmpeg command below simply overlays the audio waveform back over the video frames. To overcome the synchronization problem, first, we have to know the nature of it. Twig, After trying a few random things, I managed to make the audio/video sync by changing the rate of the audio: ffmpeg -i witness.mov -af asetrate=48018 resampled.mkv The resampled.mkv has correct sync, but unfortunately the audio is shorter than the remaining video for a few seconds. That’s why I separate the solutions as follows. I get noticeable drift, when rendering (with NLE exclusively) the 20 FPS WMV sample from above, to any output via Blender. Another thing to note is that I tried encoding an FLV from the same source file, and there are no sync issues. Audio drift (audio progressively becomes out of sync with video). source. i have a problem with this ffmpeg conversion Comman:-r 25 -i -vcodec libx264 -preset medium -crf 15 -c:a copy