What can I try to see where the problem may lay? and audio.wav into Kdenlive via drag and drop. 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! Please make sure that the Kdenlive project has the same settings as your However, after about 8 minutes the AC-3 track begins to play slightly ahead of the video and continues to drift apart at a slow, but steady rate. Geeky Hacker wallet number: 1NaGzvbXQtM9PCduXgmFeXe8D4i5C1nDyu. I can provide the two samples, but each are about 10 seconds long which comes out to 1.1G each. into a We instructed FFmpeg to copy the video stream of the second input (the one that starts with three seconds delay) to the output file and copy the audio from input one (the one that plays with no delay). A slightly confusing part is both problems have a very similar solution that only differs in nuisances. Video and audio should have now The ffmpeg command below simply overlays the audio waveform back over the video frames. In this case, we have to delay the playing of the audio. The original TS file has perfect audio video sync right through. Drag the record.mp4 source to Video channel and click in These dv files play perfectly, no audio video sync problems whatsoever. Streaming media, at it's core, requires three basic things. /* 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 */ asked Feb 6 '19 at 1:30. I'm trying to take a ts stream to a mp4 but for some reason the end mp4 is always out of sync. factor from above. Licensing has always been an issue with encoding AAC audio as most of the encoders have had a license making FFmpeg unredistributable if compiled with support for them. Stack Exchange network consists of 177 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share … 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. Is there an easy way to do this with ffmpeg? We can calculate the speedup for the audio with ... ffmpeg -i video.mp4 -i audio.mp4 -codec copy -f mp4 muxed.mp4. Is this an audio sample issue, where 44100 into 48000 is causing some frame sync problem in the render chain? Something like the following: **Update: render to libdv seems to work, without this issue of sync drift, only tested on small 15m junk, file is big! I have a B.Sc. There should be just a muted video channel and delete the audio channel. The more I work with FFmpeg, the more I discover its capabilities and realize how powerful it is. channel. i have a problem with this ffmpeg conversion Comman:-r 25 -i -vcodec libx264 -preset medium -crf 15 -c:a copy .avi the problem is that the audio is out of sync Afterwards we import audio_streched.wav into Kdenlive via drag That’s why I separate the solutions as follows. Next I have set my webcam in OBS to use my headset mic as dedicated audio input source (this ensures sync between webcam and voice audio). It is a 24000/1001 (NTSC) MPEG2 sync check file, with every 24th frame showing a coinciding tone and white flash. So far I covered many functionalities of FFmpeg besides the conventional format conversions. We are pushing an rtmp stream to our nginx+ffmpeg transcoder. Here the assumption is the audio is ahead of the video for three seconds. video. Afterwards click in the menu item Timeline on Ungroup Clips With a couple of attempts, you should get a good result. You can play with some offset flags in ffmpeg, but you kinda have to get lucky and it will eventually drift off anyways. The audio sync problem happens in both places. Grunt, 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. diff -ur ffmpeg/ffmpeg.c ffmpeg-wg/ffmpeg.c Until sometime last year, audio streams were always the "master" in ffmpeg when it came to synchronization. Regards, Wolfram. ffmpeg usage. - av_strlcatf(args, sizeof(args), ":m ax_soft_comp=%f", audio_sync_method/(double)ist->st->codec->sample_rate); What happens is the second input which we take its audio starts with three seconds delay. All audio drifts together -- that is, all audio tracks remain in sync with each other, but drift relative to video imagery. 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. It gets easy once you learn how each switch works. I have of course disabled the mic input in OBS. I've googled extensively, but still can't seem to find the issue. https://superuser.com/questions/982342/in-ffmpeg-how-to-delay-only-the-audio-of-a-mp4-video-without-converting-the-au, Resolving Google Chrome error your preferences cannot be read on Ubuntu, Sharing computer internet with HTC phones in Ubuntu, High-performance data fetching using Spring Data JPA Stream, How to fix Bluetooth protocol not available in Manjaro, Test Spring Kafka consumer and producer with EmbeddedKafka, Control threads number in Java parallel stream, How to seek Kafka offset in Spring Kafka Listener, Why JVM does not release unused memory eagerly, a discussion, Spring transaction with multiple datasources, The audio is ahead of the video (or the video behind the audio), The audio is behind the video (or the video ahead of the audio). The following command will extract the audio of the MPEG-4 into a WAV file. I'd also be interested in any other options such as the Wolfson audio card. For this fix, we have to start playing audio earlier. ffmpeg reads the video from /dev/video1, and the audio from tcp://localhost:55555. Here a small solution to fix this problem with the help of Sadly the This is wierd for 2 reasons: This ONLY happens with ffmpeg created MP4 and MKV files. As a rough guess, audio is about 1/2 second ahead after a couple of hours. 肖谋 gmail.com> writes: > I have a mp4 file 1.mp4 in which the audio is about > 2 seconds ahead of video. Good work! Extract audio with FFmpeg. Starts off in sync and gradually drifts. Like Like. Audio drift (audio progressively becomes out of sync with video). My name is Gordon Lesti. If you don’t know the exact delay, unfortunately, there’s no easy way rather than trial and error. In the example, we added three hundred milliseconds delay to the video. The audio and video sometimes end up out of sync by a small difference (less than 1 second I'd say, although it might be worse with longer recordings). Note that this filter is not FDA approved, nor are we medical professionals. I am not sure what cause this, because sometimes i don’t have this problem, but lately is been a constant. This is wierd for 2 reasons: This ONLY happens with ffmpeg created MP4 and MKV files. I'm trying to use this option because the audio is drifting out of sync with the video slowly over an hour. audio_streched.wav. 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. 1) Constant frame rate. Enabling "Audio: use only first PTS for sync" makes it out of sync. I get noticeable drift, when rendering (with NLE exclusively) the 20 FPS WMV sample from above, to any output via Blender. With the patch below, the audio drift correction (-async N, N>1) actually seems to work. TS to MP4 Audio Sync issues. For the simplicity sake, in all the given examples, we pass 3 to -itsoffset. Nor has this filter been tested with anyone who has photosensitive epilepsy. ffmpeg -h long; ... -async audio sync method-adrift_threshold threshold audio drift threshold-copyts copy timestamps-start_at_zero shift input timestamps to start at 0 when using copyts-copytb mode copy input stream time base when stream copying Please note that s/25 is something like a variable I have tried changing the framerates on both raspivid & ffmpeg with no success. by the amount of s/25 from record.mp4. Rendering out video + audio via ffmpeg produces audio that doesnt stay in sync. I can calculate for both file the amount of 1/25 seconds with the following FFmpeg and its photosensitivity filter are not making any medical claims. ffmpeg usage. However, the audio from the stream as a whole still drifts out of sync ever so slowly. These dv files play perfectly, no audio video sync problems whatsoever. Vital Stats: kdenlive 0.9.6 melt 0.9.0 ffmpeg 1.2.3 Debian 'unstable' 32-bit The ffmpeg command below simply overlays the audio waveform back over the video frames. audio bit_rate=64000 sample_rate=44100 channels=2 An odd issue has arisen. I've tried a variety of settings, including async and vsync, and nothing seems to fix the problem. Not sure what piece of the puzzle i am missing. 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. source. 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. 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). It is a 24000/1001 (NTSC) MPEG2 sync check file, with every 24th frame showing a coinciding tone and white flash. And I'd also be interested in any other options such as the Wolfson audio card. Kdenlive Originally I was using a single command for capture/encode. audio.wav have different length. In this YouTube video, I explain how to synchronize audio and video with FFmpeg. I am having an issue and am not sure if I am allowed to ask here. 44.1kHz vs 48kHz has nothing to do with the drift. The resulting file plays fine in VLC but does not in Flash or Quicktime. for a twenty-fifth of a second. With FFmpeg you can do screen casting, podcast recording, cutting files and even mixing audio and video files. Yet, there is much more to FFmpeg. Another thing to note is that I tried encoding an FLV from the same source file, and there are no sync issues. ffmpeg -h long; ... -async audio sync method-adrift_threshold threshold audio drift threshold-copyts copy timestamps-start_at_zero shift input timestamps to start at 0 when using copyts-copytb mode copy input stream time base when stream copying

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