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H264 & 5.1 surround audio



Hi, some advice needed here. I have an H264 encoded quicktime with 5.1 AAC audio. When I play it back the video slightly stutters every few seconds, short enough to almost not be noticeable sometimes, like it's skipping just a frame or two. I'm wondering if this is a card issue or a compression issue? The card we're using is class 4. I noticed that the audio is set for average bit rate, does the bright sign support that, or should it be constant or vbr? The audio sounds like it's playing correctly though. The Brightsign is set to playback at 1080i @ 59.97. Thanks for any advice. Here are the quicktime's specs: Quicktime mainconcept H264 1920x1080 @ 23.976 fps multipass target data rate 20,000 Kbps max data rate 24,000 Kbps level 4.1 High profile key frames every 24 frames auto key frame on scene change frequent CAVLC entropy encoding use B-pictures 3 use B-slices as reference unchecked multiple slices 0 reference frames 2 AUDIO AAC 5.1 surround 48 kHz average bit rate target bit rate: 320 kbps sample size 16

13 comments

  • 0
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    RokuLyndon


    It could be a card issue. You can try lowering the bitrate on your video to 20Mbps, or 16Mbps to see if it works better. Is your original source content 23.98? If not, I would recommend encoding at 29.97 or 30fps. Also, if your display supports it, 1080p @29.97 is the best 1080 output from the BrightSign.

    I'm posting some specs from episode encoder settings to see if it helps..

    Encoded using Episode Pro v5
    Encoded to MPEG-TS

    General/System Packets: Default

    Video Encode: H264
    Audio Encode: Lame MP3 or AAC-HE


    VIDEO
    General Tab

    Video Settings;
    Frame Rate: 29.97
    Size: 1920 x 1080

    Bandwidth Control: Padded CBR
    Average rate: 16,000 kbit/s

    Keyframe control: Natural & Forced Keyframes Keyframe Distance: 30 Number of Reference Frames: 2 Number of B-frames: 1

    Profile & Quality Tab

    Encoding Profile: Main
    Entropy Coding: CAVLC

    Quality Settings
    Use 2-pass encoding: ON
    2-pass interval: 242 (don't set this to high it can cause problems) Encoding Speed vs Quality: 100 (high quality)

    Use deblocking filter: ON

    Advanced Tab
    Defualt for all settings


    AUDIO

    Encoding type: Bitrate Based
    Bit Rate 128 Kbit/s
    Standard settings


    Also it is very important to note.., at data rates of 14Mbps+ you'll need a decently fast SD card or you might run into problems with dropped audio as well as other possible playback issues.


  • 0
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    Per Argentine


    The source is 1080p23.976.

    I tried a test last night dropping the target bitrate to 18,000 with a max of 20,000, and changing audio to constant bitrate, with no luck.

    I remember that I had encoded a video a few months ago with the exact same settings except as an 720p H264 mp4 file with stereo audio, which played fine.  Same bitrate, profile, etc and playing back from the same SD card.  I would do the same for this project but my encoder won't encode 5.1 surround with an mp4 file (sorenson squeeze).
  • 0
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    Per Argentine


    OK, disregard my previous post.  I was just fooling around with Squeeze's settings, and it looks like when I choose an H264 mp4 file and set the audio bit rate higher, the choice for 5.1 surround appears.  I'll do a test at 1080p23.976 with 5.1 audio and report back.
  • 0
    Avatar
    Per Argentine


    I just did several tests with H264 encoded quicktime, mp4, and ts files, and all appeared to start stuttering at the same point in the video, regardless of the bit rate (I lowered it to see if it was a card issue).  I was stumped until I came across a forum post about CUDA acceleration, and it causing problems with Brightsign.  Just now I did a test, an mp4 without CUDA, and it appears to playback fine.  Next I'll try my original quicktime settings but without CUDA.  I don't remember if I had enabled CUDA when I encoded that video a few months ago that worked, but I bet that it wasn't.
  • 0
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    RokuLyndon


    Where is the Cuda setting in your software?
  • 0
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    Per Argentine


    You can turn on CUDA in the preferences, and then when you select a codec you have the options of (for instance) mainconcept & mainconcept CUDA.

    Like I mentioned, a lower bitrate without CUDA seems to playback.  I re-encoded without CUDA but at my original bitrate of 20K with 22k max, bought two new cards to test, but neither worked.  No matter what, the video begins to stutter in the same spot a few minutes in.  The cards are a Sandisk Ultra class 6 (30MB/s they claim) and a PNY Pro class 10 (20MB/s they say).

    Now I'm encoding the video again at 17k with max 19.5k with and without CUDA just to be safe.  Whichever works I suppose will be the setting I use for the other videos.  Would be nice to get a higher bit rate though, this show has a lot of nice scenics and wildlife.
  • 0
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    RokuLyndon


    If you're doing surround, you might be better off trying mpeg2.

    BUt, if you can send a clip that shows this stutter, we can look at it.
  • 0
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    Per Argentine


    The video is 17 minutes long and about 2GB.  The stuttering begins to occur about 3 minutes in. I just tried encoding about a 1 minute section around the stuttering bit but it plays fine if the file only comprises that section.  I can send a link to the full video if you don't mind downloading it all.

    The only way I can seem to get the whole video to play is if I lower the bit rate to 15K with a 17K max to be safe.  Last night I also tried keeping the bit rate at 20K and 22K max but lowered key frames to about every 100 with no luck.

    If I go the MPEG2 route, what are the recommended settings for bit rate, profile, level, etc?  Thanks for the help.
  • 0
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    Per Argentine


    Just did one final test with the bit rate set to constant at 22k, and the video plays.  Only problem I can see is that sometimes I notice the color or brightness shifting, not sure why that is.
  • 0
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    Per Argentine


    Did another test with higher constant bit rates.  The highest was 38 Mb/s and it played on the Sandisk class 6 Card.  I'm still noticing a few brightness fluctuations here and there (maybe 5 times in a 15 minute video).  They seem to happen a half second after a new shot, the brightness goes up or down very subtly and then stays constant.  I thought the television might have an ambient brightness setting, which I turned off, and I still saw the brightness fluctuations.  Any ideas?
  • 0
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    RokuLyndon


    If you can send a sample clip to test, we can see what the problem might be. What program are you using for encoding the videos?
  • 0
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    Per Argentine


    We use Sorenson Squeeze v7.  Is there an email I can send a link for the sample files to?
  • 0
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    RokuLyndon


    Send an email to our support address.
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