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  1. Member
    Join Date
    Feb 2014
    Search Comp PM
    Hi hi,

    I'm working on an iOS app that generates videos and can upload them to Youtube. However, the videos being generated are going corrupt when uploaded to Youtube, and also going corrupt when I try to do anything to them using ffmpeg. I'm trying to learn how to analyse the problem.

    The video is 20-seconds long, consisting of some movement/animation, followed by a static image for the last 5 seconds. It's 2.1MB, and it's attached to this post.

    The issue seems to be ffmpeg can't handle a video file constructed from multiple concatenated videos. (And by extension, neither can YouTube).


    1. When I play the video on my MacBook Pro (Mountain Lion) using Quicktime Player, it plays correctly -- no corruption.

    2. When I upload the mp4 to YouTube, the first part of the video (the part with animation) becomes a solid colour across the entire frame (switches between green, dark green, and grey). The final 5 seconds of the video (the final concatenated video) displays correctly.

    3. When I try converting the video from mp4 to mp4, using ffmpeg, it corrupts in exactly the same way as it does when uploaded to Youtube.
    ffmpeg command:
    $ ffmpeg -i story_0_published.mp4 -acodec copy output.mp4

    4. When I try converting the video from mp4 to mov, using ffmpeg, it corrupts in a different way -- rainbow colours instead of solid colours -- but the last 5 seconds still converts correctly.
    ffmpeg command:
    ffmpeg -i story_0_published.mp4 -acodec copy -vcodec copy -f mov

    Here's the output from ffmpeg. I'm guessing that the "multiple edit list" warning is my main problem, but what is the "top block unavailable" error? Is this a separate issue?

    $ ffmpeg -i story_0_published.mp4 -acodec copy -vcodec copy output.mp4
    ffmpeg version 2.1.3 Copyright (c) 2000-2013 the FFmpeg developers
    built on Feb 13 2014 12:11:26 with Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.1.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables --enable-avresample --enable-vda --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame --enable-libxvid
    libavutil 52. 48.101 / 52. 48.101
    libavcodec 55. 39.101 / 55. 39.101
    libavformat 55. 19.104 / 55. 19.104
    libavdevice 55. 5.100 / 55. 5.100
    libavfilter 3. 90.100 / 3. 90.100
    libavresample 1. 1. 0 / 1. 1. 0
    libswscale 2. 5.101 / 2. 5.101
    libswresample 0. 17.104 / 0. 17.104
    libpostproc 52. 3.100 / 52. 3.100
    [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fae98806600] multiple edit list entries, a/v desync might occur, patch welcome
    [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7fae98806600] Concatenated H.264 or H.265 might not play correctly.
    Last message repeated 1 times
    [h264 @ 0x7fae98836000] top block unavailable for requested intra4x4 mode -1 at 3 0
    [h264 @ 0x7fae98836000] error while decoding MB 3 0, bytestream (6090)
    [h264 @ 0x7fae98836000] concealing 2304 DC, 2304 AC, 2304 MV errors in I frame
    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'story_0_published.mp4':
    major_brand : mp42
    minor_version : 1
    compatible_brands: mp41mp42isom
    creation_time : 2014-02-11 04:34:39
    Duration: 00:00:20.32, start: 0.000000, bitrate: 847 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1024x576 [SAR 1:1 DAR 16:9], 708 kb/s, 20.56 fps, 25 tbr, 90k tbn, 180k tbc (default)
    creation_time : 2014-02-11 04:34:39
    handler_name : Core Media Video
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 166 kb/s (default)
    creation_time : 2014-02-11 04:34:39
    handler_name : Core Media Audio

    In case it's useful, I also ran mediainfo on my source video file, but again I don't really know what to look at in here to analyse:

    $ mediainfo story_0_published.mp4
    Complete name : story_0_published.mp4
    Format : MPEG-4
    Format profile : Base Media / Version 2
    Codec ID : mp42
    File size : 2.05 MiB
    Duration : 20s 318ms
    Overall bit rate : 848 Kbps
    Encoded date : UTC 2014-02-11 04:34:39
    Tagged date : UTC 2014-02-11 04:34:39

    ID : 1
    Format : AVC
    Format/Info : Advanced Video Codec
    Format profile : High@L3.1
    Format settings, CABAC : Yes
    Format settings, ReFrames : 2 frames
    Codec ID : avc1
    Codec ID/Info : Advanced Video Coding
    Duration : 20s 318ms
    Source duration : 21s 203ms
    Bit rate : 742 Kbps
    Nominal bit rate : 1 000 Kbps
    Width : 1 920 pixels
    Height : 1 072 pixels
    Display aspect ratio : 16:9
    Frame rate mode : Variable
    Frame rate : 20.563 fps
    Minimum frame rate : 8.333 fps
    Maximum frame rate : 25.000 fps
    Color space : YUV
    Chroma subsampling : 4:2:0
    Bit depth : 8 bits
    Scan type : Progressive
    Bits/(Pixel*Frame) : 0.018
    Stream size : 1.79 MiB (87%)
    Source stream size : 1.79 MiB (87%)
    Title : Core Media Video
    Writing library : x264 core 130 r2273 b3065e6
    Encoding settings : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=0 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=25 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=abr / mbtree=1 / bitrate=1000 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=17500 / vbv_bufsize=17500 / nal_hrd=none / ip_ratio=1.40 / aq=1:1.00
    Encoded date : UTC 2014-02-11 04:34:39
    Tagged date : UTC 2014-02-11 04:34:39
    Color primaries : BT.709
    Transfer characteristics : BT.709
    Matrix coefficients : BT.709

    ID : 2
    Format : AAC
    Format/Info : Advanced Audio Codec
    Format profile : LC
    Codec ID : 40
    Duration : 16s 602ms
    Source duration : 12s 678ms
    Bit rate mode : Constant
    Nominal bit rate : 256 Kbps
    Channel(s) : 2 channels
    Channel positions : Front: L R
    Sampling rate : 44.1 KHz
    Compression mode : Lossy
    Source stream size : 258 KiB (12%)
    Title : Core Media Audio
    Encoded date : UTC 2014-02-11 04:34:39
    Tagged date : UTC 2014-02-11 04:34:39
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  2. Member Cornucopia's Avatar
    Join Date
    Oct 2001
    Deep in the Heart of Texas
    Search PM
    How are you concatenating? Because my guess would be that you are taking a shortcut (binary file concat) and that is likely the cause of the problems you are seeing. I have said this a number of times before on this site: proper joining can only be done when care is taken to strip and then correctly rebuild the (now new & aggregated ) headers & metadata.

    Also, it ought to go without saying, but keeps needing to (because it is so often foolishly ignored): all elements to be joined must be identical in their format(s), differing only in their lengths & bitrates.

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  3. Main problem seem to be that lav doesn't support the video, try to playback the content with ffplay and you see a lot of errors.
    -> How did you create the file? If you used, like Cornucopia guessed, a simple binary copy you got your problem. (concatenating stuff via binary copy is normally a bad idea)
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  4. iOS movies are long GOP variable frame rate. This is an efficient strategy for creating (relatively) small sized, (relatively) high quality videos that can be shared device to device. It sucks for editing.

    As you have discovered, to join files without reencoding allows for playback, sometimes, under only the most specialized of circumstances. You need to edit and reencode to make the files useful.

    On a mac your choices are FCPX, iMovie or Premiere. On a PC almost any NLE will work. Yes, you will lose quality, but the alternative is a useless file.
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  5. Member
    Join Date
    Feb 2014
    Search Comp PM
    Concatenation is being done using AVMutableComposition and AVVideoExport (iOS classes).

    Progress. We've now discovered that the first and last videos (which were generated on a desktop, not by the app) were causing the video to be corrupted. These two videos are just a single frame played for 5 seconds (intro & outro components). So now we just need to track down what's causing those to dislike the rest of the video segments (maybe they are in mismatched formats or codecs, like you say Cornucopia). And potentially generate new videos of those static frames with some ffmpeg magic.

    I'll try diffing the output of mediainfo from the different video segments and see if there's any obvious differences.
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