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• ffmpeg video and audio out of sync, slower (44100 to 48000)

  11 janvier 2021, par Derel

  I downloaded few live videos from Twitch using a youtube-dl command, but in the original video the audio have sampling rate in 48000 and youtube-dl saved the video in 44100, turning the video slower and the audio pitched. When i opened the audio on audacity and change the sampling rate 44100 to 48000, the timing and pitch of the audio was fixed, but my question is : Someone here knows how to fix it these files using ffmpeg, fixing the video running time and the audio pitch ?

  


  Well, I would like to have a command that I could fix just by rendering without converting the file, but if it's the only solution is converting, I accept.

  


  Thank you for you time, and I appreciate your attention !

  


• Best way to precisely trim and concatenate with ffmpeg

  24 janvier 2021, par TommyG

  I'm trying to find the most efficient way to cut up a video with frame precision then join the pieces together and have it play without any issues or glitches. But so far my experiments have failed and I can't figure out where I'm going wrong. First of all I understand that the only way to get the video cut precisely unless all frames are I-frames is to re-encode it and that's fine except to my surprise the cuts on the clips I tried are not accurate despite of re-encoding. Here's my code.

  


  ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=start_frame=23:end_frame=343,setpts=PTS-STARTPTS[cp1]; \ 
[0:v]trim=start_frame=2905:end_frame=3248,setpts=PTS-STARTPTS[cp2]; \
[cp1][cp2]concat[out]" -map [out] -c:v libx264 -crf 8 -preset ultrafast -fflags +genpts output.mkv -y


  


  When I play this the second clip [cp2] appears like it's been cut at least one frame earlier resulting in an unwanted flash. So for my second test I tried something simpler. First I opened the input file in MPC to get timing info for frames of cp2 start_frame=2905 is 00:02:01.162 and end_frame=3248 is 00:02:15.512. So I tried the following.

  


  ffmpeg -i input.mp4 -ss 00:02:01.162 -to 00:02:15.512 -c:v libx264 -crf 8 -preset ultrafast -fflags +genpts output.mkv -y


  


  The result was exactly the same with cut happening earlier than specified. Note : the -to time is actually the end of the clip. Finally someone has suggested to force key frames by specifying your cuts time stamps first like :

  


  ffmpeg -i input.mp4 -force_key_frames 00:02:01.162,00:02:15.512 output.mp4


  


  Then take the output.mp4 and feed it as input to the code where I use the filter_complex but unfortunately this returned the same results.

  


  I'm still very new to ffmpeg. What can I try next ?

  


• How to execute fluent-ffmpeg commands from express router ?

  27 janvier 2021, par Chris

  so I'm trying to control and m3u8 playlist using data sent in thru an express route and keep getting the same error "Error : ffmpeg exited with code 1 : Conversion failed !" when attempting.

  


  My code looks like this

  


  ch1Router
    .route("/source")
    .post(jsonBodyParser, (req, res, next) => {
        //video url from request body
        const { url } = req.body;
        
        //test console log
        console.log(req.body);

        //ffmpeg commands
        ffmpeg(url)
            .output('videos/Ch1.m3u8')
            .on('error', (err) => {
                console.log("Something Happened:", err.message)
                res.send("Error changing input!")
            })
            .run()
            

        
        res.send("hi")
    })


  


  When I run this exact command in a separate file using Node, the command executes and I only need to refresh my browser to see the new video file. When trying to chain it to a post request containing the video URL I get the conversion error. Any help would be appreciated.

  


  **Updated my code to prevent the server from crashing and respond with an error message but still don't understand the conversion error.