Hot answers tagged

24 votes
Accepted

How to fade in/out a video/audio clip with unknown duration?

#1 To simultaneously fade the audio in/out: ffmpeg -i clip.mp4 -vf 'fade=in:0:30,fade=out:960:30' -af 'afade=in:st=0:d=1,afade=out:st=32:d=1' -c:v libx264 -crf 22 -preset ...
user avatar
  • 30.2k
23 votes
Accepted

Adobe Premiere - Restore Audio to A/V Clip After Deleting

There's a semi-automatic way to do this – semi automatic because it involves only typing three keystrokes over and over: xf,, xf,, xf,… — you could train your cat to do it! Here's how it goes: make ...
user avatar
  • 13.4k
22 votes
Accepted

What is KeyInt and min-keyint and no-scenecut

The frames in your H.264 video are grouped into units called GOPs (Group Of Pictures). Inside these GOPs frames are classified into three types: I-frame: frame that stores the whole picture P-frame: ...
user avatar
  • 658
15 votes

How to fade in/out a video/audio clip with unknown duration?

It's a terrible hack, but this might work if all you want to do is audio fade in/out but don't know exactly how long the clip is: ffmpeg -i input.mp4 -filter_complex "afade=d=0.5, areverse, afade=d=0....
user avatar
11 votes

Timestamps are unset in a packet for stream 0. This is deprecated and will stop working in the future. Fix your code to set the timestamps properly

The usual solution for this situation: -fflags +genpts It should eliminate the warning, but there's no guarantee your sync issues will be solved.
user avatar
10 votes
Accepted

Can video have multiple streams (like it has 2 audio streams)

Yes. MPEG-4 Part 14 (the MP4 container format) supports any number of objects (e.g. video, audio and subtitle streams) and isn't limited to only one stream per content type. In practice however, you ...
user avatar
  • 5,382
9 votes
Accepted

ffmpeg concat introduces a/v sync problem

Run ffmpeg -i titlefile.mp4 -vf setdar=16/9 -video_track_timescale 29971 -ac 1 newtitle.mp4 and then run concat with the new title video. Modern containers like MP4 have Presentation TimeStamps, ...
user avatar
  • 30.2k
8 votes

What's the benefit of using an external audio recorder compared to an internal one?

There are a variety of reasons to have an external recorder depending on the size of your production. A big advantage is the number of audio inputs and the ability to record each of those inputs as ...
user avatar
8 votes
Accepted

Loudness control LUFS level adjustments

FFmpeg's loudnorm filter can be used. Basic syntax is ffmpeg -i in.mp4 -c:v copy -af loudnorm=I=-23:LRA=1 -ar 48000 out.mp4 The loudness range (LRA) should be 2 x max deviation. Also see the ...
user avatar
  • 30.2k
8 votes
Accepted

FFMPEG: Loop video to the length of audio

For video, stream_loop option should be used. ffmpeg -y -stream_loop -1 -i video -i audio.mp3 -fflags +shortest -max_interleave_delta 50000 -c copy output.mp4 You'll have to use a very recent ...
user avatar
  • 30.2k
6 votes

ffmpeg: Normalize audio in an avi file

You can use ffmpeg with the compand audio filter (a port of sox effect filter of same name) to "compress or expand the audio's dynamic range", but admittedly this is one of the more ...
user avatar
  • 9,219
6 votes
Accepted

App to quickly analyze audio loudness of several video files?

ffmpeg, a free multi-platform command-line tool, can do this. Use the volumedetect and EBUR filters on each of the files ffmpeg -i input.mov -af volumedetect,ebur128 -f null - 2> input.log This ...
user avatar
  • 30.2k
6 votes
Accepted

Do I need an audio recorder?

Back in the day when movie cameras recorded to film, the sound made by the cameras was something to be isolated from the sound recording process. Digital video cameras make very little noise (with ...
user avatar
6 votes

How to modify audio level of video according to replaygain info?

FFmpeg, a free command-line tool, has a volume filter that should do this. Syntax would be ffmpeg -i input.mp4 -c:v copy -af volume=replaygain=track output.mp4 The af invokes the volume filter with ...
user avatar
  • 30.2k
6 votes
Accepted

Mono to Stereo using FFMPEG

If you run ffmpeg -layouts, you will see that stereo indicates the presence of two channels, one assigned as Front Left and the other as Front Right. If you use -ac 2 in your encode, ffmpeg will ...
user avatar
  • 30.2k
6 votes

What is KeyInt and min-keyint and no-scenecut

Most video encoders apply temporal compression i.e. most frames only store the difference in image content relative to other frames, thus saving storage space, while a few frames store the whole image....
user avatar
  • 30.2k
5 votes
Accepted

Is automatic switching of audio stereo balance while cutting between camera angles possible?

Is it possible? Sure, just setup each source clip as a sequence that has the audio feed you want for that shot and leave the tracks linked so that you cut between both video and audio. Is it ...
user avatar
  • 19.2k
5 votes

What's the benefit of using an external audio recorder compared to an internal one?

Yes, its way better. Being able to monitor the levels, and headphones, makes a huge difference. However, its not even just the quality of the mic or recording device its the location. Having an ...
user avatar
  • 251
5 votes

Will Compression/Format of Audio Change when Uploaded to YouTube?

Youtube generally reencodes all videos you upload to youtube to ensure compatibility across various platforms and to provide smaller versions of the videos for users with slow internet connections. So ...
user avatar
  • 5,382
5 votes
Accepted

Handle 2 sources in a video file

First, get ffmpeg. Generally, you want to give YouTube the highest quality you can because it will re-encode anything you give it, but the formats used in MXF can be mental for uploading. So re-...
user avatar
  • 9,219
5 votes
Accepted

Does the MP4 HTML5 compatible video type allow for mono audio?

The Mainconcept or Sony codecs in Vegas are subpar for low-bitrate output such as needed for HTML5 use. Use ffmpeg to generate your HTML5 videos. Yes, mono audio is acceptable for HTML5 use, but once ...
user avatar
  • 30.2k
5 votes
Accepted

How to precisely synchronise an audio and video track from separate devices?

First off, if you have audio with your video (that you want to replace with your high-quality audio recording), then step #1 is to nudge the Zoom audio track to line up the impulse of the clap with ...
user avatar
5 votes
Accepted

By how much can video and audio be out of sync?

There are, in fact, several standards on audio/video or lip sync. The problem is, they can't all agree on what the acceptable error is. What is well understood is that if the audio lags the video it ...
user avatar
5 votes
Accepted

Are most scenes in movies voiced over in post production?

It's generally preferred to use the actual dialog audio from the take. It matches the movement of the lips, it sounds right for the environment, the actor is giving an authentic performance, etc. ...
user avatar
4 votes
Accepted

How to detect and extract words from audio/video stream online in a webpage itself?

If you work on a regular basis with the "owner" of the voice I can recommend Nuance's Dragon it offers very accurate speech to text with very few errors but it needs some "calibration" to a specific ...
user avatar
  • 7,109
4 votes

Cannot mark my video with CC SA licence because Youtube Content ID found 3rd party soundtrack which itself is CC SA licensed

I am not a laywer, but my limited understanding of the situation is this. I see two issues here: When you upload a video to youtube you need to grant them certain rights. As Youtube is without any ...
user avatar
  • 604
4 votes
Accepted

Will I lose quality when converting avi to mkv?

AVI and MKV are both containers, so in theory it should be possible to transfer your contents with no further loss. I can't say for certain if MKV can wrap xvid4, but it's very likely. You shouldn't ...
user avatar
  • 4,654
4 votes

Will I lose quality when converting avi to mkv?

As Jim Mack has correctly pointed out MKV (Matroska) and AVI are containers, and are both able to store many of the same streams without any change to the streams themselves, and thus the remuxing ...
user avatar
  • 810
4 votes

What's the benefit of using an external audio recorder compared to an internal one?

Can't speak for the Nikon, but the Canon 5D and 7D both have terrible on-board audio, with no way to easily monitor the audio levels. The Zoom will have a better mic pre-amp, and will let you monitor ...
user avatar
  • 6,398
4 votes

Places to look for sound tracks for videos

I've used AudioMicro.com and like a lot of their music. I hear good things about incompetech.com. You can also just Google "royalty-free music sites" and you'll find several, each with different ...
user avatar
  • 1,589

Only top scored, non community-wiki answers of a minimum length are eligible