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  1. I'm trying to edit a recording in AVIDemux, but there's a problem with the audio. It plays fine in VLC, and some commercials are OK. But the main program and other commercials just have a faint bit of background audio, and no main voices.

    File info, according to VLC:
    Stream 0
    Type: Video
    Original ID: 4113
    Codec: H264 - MPEG-4 AVC (part 10) (h264)
    Resolution: 1920x1090
    Display resolution: 1920x1080
    Decoded format: Planar 4:2:0 YUV
    Stream 1
    Type: Audio
    Original ID: 4352
    Codec: A52 Audio (aka AC3) (a52)
    Channels: 3F2R/LFE
    Sample rate: 48000 Hz
    Bitrate: 384kb/s


    File info, according to AVIDemux:
    Video
    Codec 4CC: H264
    Image size: 1920x1080
    Aspect Ratio: 1:1 (1:1)
    Frame Rate: 59.940 fps
    Total Duration: 00:11:36.178
    Extra Video Properties
    ExtraDataSize: 00
    Extra data: (blank)
    Audio
    Codec: AC3
    Channels: Stereo
    Bitrate: 24000Bps/192kbps
    Variable Bitrate: (blank)
    Frequency: 48000 Hz
    Total Duration: 00:11:35.242


    Any suggestions would be appreciated.
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  2. The downmix from 5.1 to 2.0 is being done incorrectly. The center channel is being left out.
    Last edited by jagabo; 18th Oct 2015 at 21:04.
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  3. I'm the one making the recordings. Doing it the say way as the past several months, but this problem just cropped up. So I'm uncertain what could have caused it.

    I think the original broadcast is in stereo, but it's coming over SPDIF for audio (video is Component, FYI). If it is getting the channels mixed up, how do I fix it?
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  4. Maybe the channels are in an unusual order. Open the audio track in a multichannel audio mixer and downmix yourself. Audacity with the ffmpeg source plugin can open audio from most AV containers. It doesn't mux into AV files so you'll have to save it in an audio format and import it into your AV muxer.
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  5. I opened it with Audacity, but it seems the same as playing it in AVIDemux. It shows two channels, but when I play I get no vocals (which I can get fine with VLC).

    I'm not very good with Audacity, so I could use some guidance. The info for the track shows Stereo, 48000Hz, 32-bit float. Balances are in the middle. If I click the down arrow next to the track name, there is a mark on Left Channel, but it's greyed out (as are the Mono, Right Channel, and Make Stereo Track options).

    Any suggestions?
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  6. Using that pulldown select Split Stereo to get separate left and right channels. Play the audio but Mute or Solo one of the channels. Do you hear the dialog now?
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  7. Sorry, no. Both tracks sound identical, and there are long gaps where there should be talking (without background audio) which are completely silent.
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  8. Are you sure VLC isn't getting audio from another file? Media players can be set to automatically load audio from a separate file with the same base name. So if you have a video named MyVideo.MP4 and an audio file named MyVideo.AC3 VLC might be playing the audio from MyVideo.AC3.
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  9. Positive. I've been doing this exact same process for months. Also, to remove any doubt, I didn't have Audacity on the computer I recorded the video on, so I copied the file to another system that did. I only transferred one file (and the source location isn't shared, so the 2nd PC couldn't be pulling stuff over the network).
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  10. The only thing left I can imagine is that there's something wrong with the header that's confusing everything except VLC.
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  11. Could it have to do with VLC seeing the audio channels as 3F2R/LFE, while AVIDemux & Audacity seem to see Stereo?
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  12. Originally Posted by Joker41NAM View Post
    Could it have to do with VLC seeing the audio channels as 3F2R/LFE, while AVIDemux & Audacity seem to see Stereo?
    Of course. There must be something unusual in the header that's making other reader/splitters see the audio as two channels instead of six. Your descriptiong "faint backgound audio" makes it sound like only the rear channels of the 5.1 source are being detected. You might try remuxing with ffmpeg or Mkvtoolnix to see if that corrects the header info so that other programs see it as 5.1. I doubt remuxing with ffmpeg will help because the ffmpeg source plugin for Audacity saw it as two channel. But mkvtoolnix might work.

    Can you post a full text MediaInfo report of the source video?
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  13. Here's the MediaInfo report:
    Code:
    General
    ID                                       : 0 (0x0)
    Complete name                            : <redacted>\HDPVR2_20151018_2105.ts
    Format                                   : MPEG-TS
    File size                                : 7.50 GiB
    Duration                                 : 1h 31mn
    Overall bit rate mode                    : Variable
    Overall bit rate                         : 11.8 Mbps
    
    Video
    ID                                       : 4113 (0x1011)
    Menu ID                                  : 1 (0x1)
    Format                                   : AVC
    Format/Info                              : Advanced Video Codec
    Format profile                           : High@L4
    Format settings, CABAC                   : Yes
    Format settings, ReFrames                : 3 frames
    Codec ID                                 : 27
    Duration                                 : 1h 31mn
    Bit rate                                 : 11.0 Mbps
    Width                                    : 1 920 pixels
    Height                                   : 1 080 pixels
    Display aspect ratio                     : 16:9
    Frame rate                               : 29.970 fps
    Standard                                 : Component
    Color space                              : YUV
    Chroma subsampling                       : 4:2:0
    Bit depth                                : 8 bits
    Scan type                                : Interlaced
    Scan order                               : Top Field First
    Bits/(Pixel*Frame)                       : 0.177
    Stream size                              : 7.00 GiB (93%)
    Color range                              : Limited
    Color primaries                          : BT.709
    Transfer characteristics                 : BT.709
    Matrix coefficients                      : BT.709
    
    Audio
    ID                                       : 4352 (0x1100)
    Menu ID                                  : 1 (0x1)
    Format                                   : AC-3
    Format/Info                              : Audio Coding 3
    Mode extension                           : CM (complete main)
    Format settings, Endianness              : Big
    Codec ID                                 : 129
    Duration                                 : 1h 31mn
    Bit rate mode                            : Constant
    Bit rate                                 : 192 Kbps
    Channel(s)                               : 2 channels
    Channel positions                        : Front: L R
    Sampling rate                            : 48.0 KHz
    Compression mode                         : Lossy
    Delay relative to video                  : -458ms
    Stream size                              : 125 MiB (2%)
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  14. I tried MKVToolnix and FFMpeg. MKVToolnix wouldn't open the file (probably because it was a .ts, which it doesn't recognize).

    However, FFMpeg opened it, and seemed to have the correct audio when I played a brief clip. I'm trying a conversion now, and will let you know the result.
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