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  1. Hello. I have a TiVo recording that I've converted to MPEG using tivodecode. I wanted to extract a ~4-minute clip from the 1.5 hour MPEG-2 file, and everything I read said that MPEG Streamclip is the perfect app for the job. When I load the MPEG into MPEG Streamclip, it plays fine. MPEG Streamclip shows the following information:

    Video PID: 224 (MPEG-2, 1920 × 1080, 16:9, 29.97 fps, 8.00 Mbps, upper field first)
    Audio PID: 128 AC3 3/2 (48 kHz, 384 kbps)
    Audio Mode: Stereo Mix

    After marking a clip using I and O and then selecting Trim from the Edit menu (or hitting command-T), the resulting trimmed clip has no audio! If I "Revert Trimming", the sound comes back, but that's no help. I've tried MPEG Streamclip versions 1.9.2 and 1.9.3b7. I've tried "Fix Timecode Breaks" (with "Do not skip any frames" checked). I also saw and tried someone's suggestion to "Convert to MPEG..." first (even though my file is already in MPEG-2 format). None of those things helped.

    What checkboxes in Preferences are recommended? I've tried "Preserve GOPs at In/Out", but that didn't help either.

    I'm using OS X 10.6.8 Snow Leopard with the latest Perian and Apple MPEG-2 QT components installed.

    Please help!

    Thanks,
    Ed
    Last edited by DarthEd; 7th Mar 2012 at 02:06.
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  2. Member
    Join Date: Jun 2003
    Location: United States
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    Why not try converting the selection to H264/AAC in an MP4 container?
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  3. Thanks for your reply. I'm trying to edit without reencoding. This is for archival purposes, and I'd rather not edit in a lossy fashion, particularly with regards to the audio.

    I'm under the impression that MPEG Streamclip supports what I'm trying to do. Am I mistaken?
    Last edited by DarthEd; 7th Mar 2012 at 02:28.
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    If you convert to H264/AAC using the same bitrate, etc. as the original footage, I doubt you'd even see a difference (considering MPEG2 is already lossy).
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  5. so you have a "DVD compliant file" (mpeg2 + ac3)
    Originally Posted by DarthEd View Post
    After marking a clip using I and O and then selecting Trim from the Edit menu (or hitting command-T), the resulting trimmed clip has no audio!
    you certainly have "too much holes" in audio track during capture
    try:
    - no trim and menu item "File" > "Convert to mpeg" (it's only a rewrap, speed and no quality lose)
    Reload the mpg file in MPSC, it's ok or not? (if not, no real hope to obtain something with MPSC )
    - another try:
    fix timecodes break first (command-F) and -once again- try to convert to mpeg without any trim. Your resulting file has audio or not?
    PS: All tries with NO CUTS FIRST

    …and give news

    What checkboxes in Preferences are recommended? I've tried "Preserve GOPs at In/Out", but that didn't help either.
    "Preserve GOP" is a good choice: if you trim inside a GOP (GroupOfPictures) you will obtain a "part of image" (not a full one), so damaged images. MPEG2 has to be trimmed at beginning or end of GOP.

    PS: all these steps are to obtain an easier file to handle first (a "corrected one" …if possible) . The trim will the the next step

    bye
    For DVD, iPad, HD, Western Digital, … iMovie & FCPX? New: MovieConverter-Studio 2.50 is available! - Handle your camcorder's videos? in 60p too? do a slow-motion? MovieCam
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  6. Thank you, Herve, for your reply. I did exactly what you suggested in the order you suggested, and I get the same result: No audio.

    First, I did "Convert to MPEG..." and saved it with a different filename. I closed the window and opened up the new file.
    Then, I selected "Fix Timecode Breaks..." (with "Do not skip any frame" checked). For the record, it doesn't seem to detect any timecode breaks in my file at all. I saved the result with a different filename. Closed the window and opened up the new file. Then I selected a clip using I and O and trimmed. When I play the trimmed section, all I hear is silence.
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  7. I tried this again with another TiVo recording, and I encountered the same problem: no AC3 audio after trimming. Could there be some interaction with the latest Perian? Could it be a bug in both MPEG Streamclip versions 1.9.2 and 1.9.3b7?
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  8. Member netmask56's Avatar
    Join Date: Sep 2005
    Location: Sydney, Australia
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    Why don't you use MPEGStreamclip to demux the file into separate video and audio tracks? You could then examine the audio and make sure it is ok. Maybe Audacity ? http://audacity.sourceforge.net/download/mac and then edit and remux together in a suitable MAC based MPEG2 editor. You can actually remux in MPEGStreamclip if you put the video and audio in a folder and point to the video track and convert to mpeg2
    Last edited by netmask56; 2nd May 2012 at 06:59.
    TheVoiceIsAnotherPerson ~ BeyonWiz DP-P1 and T3 PVR's ~ Popcorn C200 ~ Samsung ES8000 65" LED TV ~ Windows 7 ~ Yamaha RX-A1030 http://www.openwiz.org/wiki/ProjectX
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  9. Hmmm, I accidentally took the trimmed MPEG-2 file, which plays silently in both QuickTime (7 and X) and MPEG Streamclip, and converted it to MP4. I actually meant to convert the untrimmed MPEG-2, but I picked the wrong one. Well, the resulting MP4 file had sound! Media Inspector shows that the trimmed MPEG-2 file has the AC-3 audio track, but, for whatever reason, you just can't hear the audio in either QuickTime and MPEG Streamclip. So I tried playing the file with VLC, and I can hear the audio in VLC. Ditto for MPlayerX. So it's apparently only QuickTime and MPEG Streamclip where the audio is having problems.

    Thanks, netmask56, for your reply. I saved just the audio track of the trimmed file to an .ac3 file using MPEG Streamclip as you suggested. The .ac3 file played just fine in MPEG Streamclip, VLC, and MPlayerX, but when I played the .ac3 file in QuickTime 7 with Perian, I could only hear audio coming out of the left speaker.
    Last edited by DarthEd; 2nd May 2012 at 11:56.
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  10. Interestingly, if I demux the trimmed MPEG-2 file in MPEG Streamclip and then remux it with MPEG Streamclip, MPEG Streamclip can play the resulting file just fine. Weird. Still no AC3 audio in QuickTime Player though, but maybe the problem is that Perian just can't handle this format.
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  11. Member netmask56's Avatar
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    Originally Posted by DarthEd View Post
    Interestingly, if I demux the trimmed MPEG-2 file in MPEG Streamclip and then remux it with MPEG Streamclip, MPEG Streamclip can play the resulting file just fine. Weird. Still no AC3 audio in QuickTime Player though, but maybe the problem is that Perian just can't handle this format.
    Have you purchased the Quicktime MPEG2 plug in? (I don't think it comes with Quicktime-Pro) Maybe that is the problem with Quicktime playback? On a PC it is easy to just install Quicktime Alternative a free shareware program. I had to buy the MPEG2 plug in for QuicktimePro for PC..($20)
    TheVoiceIsAnotherPerson ~ BeyonWiz DP-P1 and T3 PVR's ~ Popcorn C200 ~ Samsung ES8000 65" LED TV ~ Windows 7 ~ Yamaha RX-A1030 http://www.openwiz.org/wiki/ProjectX
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  12. Yes, I have purchased the QuickTime's MPEG-2 plugin, and I have the proper Intel version of that plugin installed. I have a QuickTime Pro license key as well. The MPEG-2 video is decoded properly, but the AC3 audio apparently isn't. I don't think Apple's QuickTime MPEG-2 plugin supports AC3 audio, so I think the AC3 decoding should be done by Perian, but it only sort of works and then only sometimes, I guess. *shrug*
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  13. QuickTime never played ac3 sound inside mpeg file (with or without mpeg2 codec)
    if your only concern is "to not manage to hear audio part in QT Player" …so you have no real concern, all is normal

    PS: VLC can read it (both audio & video)
    MPSC can read it too (because it has its own ac3 decoder, it does not try to use QT's one …'cause Qt does not handle this type of audio )

    bye
    For DVD, iPad, HD, Western Digital, … iMovie & FCPX? New: MovieConverter-Studio 2.50 is available! - Handle your camcorder's videos? in 60p too? do a slow-motion? MovieCam
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  14. OK, you're right about QuickTime Player, I'm sure. I could've sworn I'd tried it in the past and Perian was able to decode the AC3 audio in an MPEG-2 file, but it seems I was misremembering.

    But there's still the issue with MPEG Streamclip. As soon as I hit command-T to trim a selection in a MPEG-2 file with AC3 audio, MPEG Streamclip cannot or will not play the audio in the trimmed clip. Other apps, such as VLC and MPlayerX don't have a problem though, so it's all good as long as I don't need to make more than one trim, I guess.
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  15. my answer is borring but… demux first, remux-trim second (this way to do seems to works with your files)
    PS: one -theorically useless- step more, but success

    bye
    For DVD, iPad, HD, Western Digital, … iMovie & FCPX? New: MovieConverter-Studio 2.50 is available! - Handle your camcorder's videos? in 60p too? do a slow-motion? MovieCam
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  16. as a side note: I generally would recommend to send mpeg2 captures through ProjectX before processing it with another tool,.. (since ProjectX is java based it should also work on Mac,.. only tried it on Linux and Windows so far myself)
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