FLV to MPEG-4

[SurreySpring]

I'm struggling with a conversion but right now I'm looking to understand rather than a quick "please can someone do this for me" question.

I have an FLV file that I'm struggling to convert to MPEG-4. In brief the audio is going out of synch after about 20 minutes or so. I'm looking at the file using Avidemux and can see that the video is H264 and the audio is AAC.

Now I'm just starting to learn about the whole container thing - I understand (or can be corrected!) that FLV is a container for audio, video, subtitle info etc as is MPEG-4/MP4. What I'd like is an MPEG-4 file with video in H264 and audio in AAC so that my media player can see it.

Now my question is, if I'm not changing the video from H264 and the audio from AAC - why is this conversion from FLV so difficult? There's obviously a major technical issue in doing the conversion as everyone is talking about it and I can't seem to find software to do it properly, but what is that issue?

[bat999]

Now my question is, if I'm not changing the video from H264 and the audio from AAC - why is this conversion from FLV so difficult?

Hi
It's not difficult.
The smart way to do the job is with FFmpeg, like this:-

ffmpeg -i filename.flv -vcodec copy -acodec copy filename.mp4

The less smart way is to extract the two tracks using FLVextract and then import them into mp4 using YAMB.

[SurreySpring]

That's not actually an option I'd tried so I gave it a go. I've been using a 4Media converter and also the Applian converter.

First time I tried it, didn't recognise ffmpeg.exe so I copied a copy into the folder to avoid path issues. Got the following error message:

[mp4 @ 04593840] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 1 >- 1
av_interleaved_write_frame(): Invalid argument

& got a 2kb output file that didn't even pretent to work!

[bat999]

. Got the following error message:

[mp4 @ 04593840] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 1 >- 1
av_interleaved_write_frame(): Invalid argument

Hi
Try FFmpeg again with the audio bitstream filter, like this:-

  ffmpeg -i filename.flv -vcodec copy -acodec copy -absf aac_adtstoasc filename.mp4

[SurreySpring]

Exactly the same error - what is that command looking to do?

[bat999]

Exactly the same error - what is that command looking to do?

The command is to copy over the video and audio tracks (direct copy).
The bitstream filter fixes the audio from flv files (sometimes).

Looks like there's problems with this flv file.
Might be good idea to use FLVextract and YAMB now.

[SurreySpring]

Just so I understand - FLVextract will leave me with a silent movie and an audio track and YAMB will allow me to join to two together by hand. Is that correct?

(BTW I have about 200 of these but I'm game for a laugh!)

[SurreySpring]

Just gave it a go - both are very easy packages to use, very intuitive and straightforward.

Ended up with an MP4 file with sound out of synch!

Is there a program that will let me get inside the video and give the sound a little yank to the left? (if you see what I mean)

[bat999]

Just so I understand - FLVextract will leave me with a silent movie and an audio track and YAMB will allow me to join to two together by hand. Is that correct?

No, FLVextract will retain your original flv file and create two extra files.... (*.h264 and *.aac).
Then you import these two new extra files into YAMB.

If you have 200 flv files available, try another of them with FFmpeg.

[SurreySpring]

Is ffmpeg the only game in town or are there alternatives?

I've done a bit of googling and this "non monotonically increasing dts to muxer in stream" seems to be a common unsolved error. Seems to be an issue with larger files which could be why I'm only seeing it on larger files and afer 20/30 minutes of play time.

[SurreySpring]

I've been playing with FLVExtract and YAMB to break up an FLV file and reassemble it (286 and AAC). I'm getting a sound and picture synch problem that I'd like to play at correcting the sound. WhenI use YAMB it simply joins the video and sound side by side - I'd like to play with the match a bit more. Doing things like stretch the sound file by a second or so over the file length or introduce a delay somewhere. Does anyone know of an application that will allow me to do this sort of playing?