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oktober 17, 2019
Container: MP4 Video stream encoding: MP4 AVC Max video resolution: 720 (the full 960 pixels can not be used) FPS: 30 Audio: 48kHZ AAC Max audio bitrate: 320 kbps Max total bitstream rate: 14Mbps
While the swedish public service television company SVT provides an Iphone app for viewing streams via internet, the quality of such streams are not as good as the DVB-T broadcasting, and at my current location I pay for internet traffic (or rather I have a maximum of some GBs/month for free which I don't want to waste on video data).
I played around with recording video from DBV-T and wanted to view the movie on an Ipod Touch 4g. Recording DBV-T is only a matter of dumping the data - which comes in MPEG-TS format, to file. Such a file has video data in 720x576 @ 25 fps 15000 kbps and audio data as mp3 192 kbps, that is at an extremely high quality. And it comes for free through the air :-)
tzap -r -H -t 5400 -o - 'SVT1 Västnytt' > the.movie.mpeg
The Ipod Touch does not support MPEG-TS, so the video as to be encoded to a supported format. First, fix any audio/video sync problems with projectx
The MPEG-TS files you get when capturing DVB-T have an negative audio offset which must be corrected for. As of 2.5, avidemux, does not handle this automatically, thus projectx is used to get the amount of offset.
A sample file my-cutpoints.Xcl, defining the cuts for a minimal file.
CollectionPanel.CutMode=0 71440 750000
projectx -cut my-cutpoints.Xcl -tom2p -out /media/disk/tv -name foo /media/disk/tv/brooks.mpeg
Now, load foo.m2p into avidemux, choose Audio —> Main Track, and there you see the offset. Choose "shift" and enter the offset.
I use avidemux and choose the following settings
ffmpeg -r 25 -maxrate 10M -b 5M -qmin 3 -qmax 31 -bufsize 4096 -g 300 -aspect 4:3 -f image2 -i '%d.png' -vcodec mpeg4 -s 800x600 chi.mp4
The video recordings are stored in PRIVATE/AVCHD/BDMV/STREAM/.
When opening a file, avidemux will warn
H264 detected If the file is using B-frames as references it can lead to a crash or stuttering. Avidemux can use another mode which is safe but YOU WILL LOSE FRAME ACCURACY. Do you want to use that mode? Cancel | *Safe Mode*Choose cancel, then you will be asked
Index is not up to date You should use Tool->Rebuild frame. Do it now? No | *Yes*Choose yes.
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Our new digital camera - EASTMAN KODAK COMPANY KODAK EASYSHARE Sport Camera, C123 - produces audio encoded with uLaw, as can be seen from the output of mplayer below:
Opening audio decoder: [alaw] aLaw/uLaw audio decoder AUDIO: 8000 Hz, 2 ch, s16le, 128.0 kbit/50.00% (ratio: 16000->32000)
This audio codec is not supported by avidemux, so use mplayer to decode the audio to WAVE-format.
mplayer -vo null -vc null -ao pcm:file=100_0025.wav /media/disk/DCIM/100KC123/100_0025.AVI
Also, the audio must be resampled to 48000 Hz from the original 8000 Hz. This can be done in avidemux, in the Filters dialog, choose Resampling, and set it to 48000.
Our first movie was showing the kids jumping from the rocks into the sea, a scene that required quite some bitrate, and I used 5000 kilo bits per second, two phase encoding.
A minimal script for decoding audio from video-clips:
#!/bin/sh mplayer -vo null -vc null -ao pcm:file=$1.wav $1
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