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• Video concatenation using ffmpeg. Output video length is longer than inputs length

  28 décembre 2022, par Rostyslav Mosorov

  I have a problem with video mp4 concatenation using ffmpeg. I have two the same videos and I want to concatenate them. I created file inputs.txt and then used command :

  


  ffmpeg  -f concat -i inputs.txt -c copy mergedVideo.mp4

  


  Output :

  


  ffmpeg  -f concat -i inputs.txt -c copy mergedVideo.mp4
ffmpeg version 5.0.1 Copyright (c) 2000-2022 the FFmpeg developers
  built with clang version 12.0.1
  configuration: --prefix=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_h_env_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_placehold_pl --cc=arm64-apple-darwin20.0.0-clang --disable-doc --disable-openssl --enable-demuxer=dash --enable-gnutls --enable-gpl --enable-hardcoded-tables --enable-libfreetype --enable-libopenh264 --enable-neon --enable-libx264 --enable-libx265 --enable-libaom --enable-libsvtav1 --enable-libxml2 --enable-libvpx --enable-pic --enable-pthreads --enable-shared --disable-static --enable-version3 --enable-zlib --enable-libmp3lame --pkg-config=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_build_env/bin/pkg-config --enable-cross-compile --arch=arm64 --target-os=darwin --cross-prefix=arm64-apple-darwin20.0.0- --host-cc=/Users/runner/miniforge3/conda-bld/ffmpeg_1649114094397/_build_env/bin/x86_64-apple-darwin13.4.0-clang
  libavutil      57. 17.100 / 57. 17.100
  libavcodec     59. 18.100 / 59. 18.100
  libavformat    59. 16.100 / 59. 16.100
  libavdevice    59.  4.100 / 59.  4.100
  libavfilter     8. 24.100 /  8. 24.100
  libswscale      6.  4.100 /  6.  4.100
  libswresample   4.  3.100 /  4.  3.100
  libpostproc    56.  3.100 / 56.  3.100
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x1561044a0] Auto-inserting h264_mp4toannexb bitstream filter
Input #0, concat, from 'inputs.txt':
  Duration: N/A, start: -0.064000, bitrate: 1424 kb/s
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 1355 kb/s, 50 fps, 50 tbr, 12800 tbn
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 16000 Hz, mono, fltp, 68 kb/s
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
File 'mergedVideo.mp4' already exists. Overwrite? [y/N] y
Output #0, mp4, to 'mergedVideo.mp4':
  Metadata:
    encoder         : Lavf59.16.100
  Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 1355 kb/s, 50 fps, 50 tbr, 12800 tbn
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 16000 Hz, mono, fltp, 68 kb/s
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame=    0 fps=0.0 q=-1.0 size=       0kB time=00:00:00.06 bitrate=   6.0k[mov,mp4,m4a,3gp,3g2,mj2 @ 0x154f28b20] Auto-inserting h264_mp4toannexb bitstream filter
frame=  166 fps=0.0 q=-1.0 Lsize=     583kB time=00:00:03.39 bitrate=1407.4kbits/s speed= 179x    
video:550kB audio:29kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.737394%


  


  Unfortunately the result is different then I expected :
  
movies comparison

  


  The output is longer than the length of two inputs. Any thoughts ?

  


  Also I tried using different commands :

  


  ffmpeg  -f concat -i inputs.txt -c copy mergedVideo.mp4


  


  or set the framerate :

  


  ffmpeg -r 50 -f concat -i inputs.txt -c copy mergedVideo.mp4


  


  What is also weird that I have the same problem when using moviepy library.

  


  from moviepy.editor import VideoFileClip, concatenate_videoclips
videos = [VideoFileClip("0.mp4"), VideoFileClip("0.mp4")]
concatenate_videoclips(videos).write_videofile('mergedVideo.mp4')


  


  Update
ffprobe command for output file

  


  ffprobe -v error -select_streams v -show_entries stream=codec_name,time_base,start_pts,start_time,duration -of default=noprint_wrappers=1 mergedVideo.mp4 
codec_name=h264
time_base=1/12800
start_pts=0
start_time=0.000000
duration=3.380000


  


  For input :

  


  ffprobe -v error -select_streams v -show_entries stream=codec_name,time_base,start_pts,start_time,duration -of default=noprint_wrappers=1 0.mp4          
codec_name=h264
time_base=1/12800
start_pts=0
start_time=0.000000
duration=1.660000


  


  The duration supposed to be 2*1.66 = 3.32 and but it's 3.38.

  


  Content of the inputs.txt

  


  file '0.mp4'
file '0.mp4'


  


• Trimmed a video with ffmpeg ; looks fine on a Mac, but audio/video are 3 seconds out of sync with Windows default player. Huh ?

  12 avril 2021, par kaltorak

  I've got a video which looks and sounds right when I play it in Windows or on a Mac.
  
I trimmed it with ffmpeg.
  
The resulting file

  


  

  • plays fine on a Mac with QuickTime

  


  • throws an error on Windows QuickTime (Error -2041 : an invalid sample description was found in the movie (myfile.trimmed.mp4))

  


  • plays with Win10's default player (Movies and TV ?), but with the audio lagging nearly 3 seconds behind the video (as determined by me counting Mississippis, nothing more precise than that.)

  


  


  My original file :

  


  ffprobe -hide_banner myfile.mpg
[h264 @ 00000253d2d762c0] Increasing reorder buffer to 2
[mpegts @ 00000253d2d6fe00] PES packet size mismatch
[mpegts @ 00000253d2d6fe00] Packet corrupt (stream = 1, dts = 8467425232).
[mpegts @ 00000253d2d6fe00] Could not find codec parameters for stream 2 (Unknown: none ([151][0][0][0] / 0x0097)): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, mpegts, from 'myfile.mpg':
  Duration: 00:30:00.63, start: 92282.982578, bitrate: 6249 kb/s
  Program 1
    Stream #0:0[0x1aab]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
    Stream #0:1[0x1abf]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, 5.1(side), fltp, 384 kb/s
    Stream #0:2[0x1ac1]: Unknown: none ([151][0][0][0] / 0x0097)
Unsupported codec with id 0 for input stream 2


  


  Stuff I notice :

  


  

  • The mpg container shouldn't hold h264 video. That messed me up, but remuxing to an mp4 container during the trimming step seemed to make it OK.

  


  • The start time isn't anywhere close to zero... but I don't think there's anything wrong with that.

  


  • The audio and video are in sync as I watch in a player, but the file contains audio starting nearly 1 second before the video. The first audio packet has pkt_pts_time=92282.982578 (matching the start reported by ffprobe, above), while the first video packet has pkt_pts_time=92283.926411

  


  


  So I trim it, like so...

  


  ffmpeg -hide_banner -ss 00:17:24 -i myfile.mpg -t 00:02:40 -c copy myfile.trimmed.mp4
[h264 @ 000002d5d73f4040] Increasing reorder buffer to 2
[mpegts @ 000002d5d73edbc0] PES packet size mismatch
[mpegts @ 000002d5d73edbc0] Packet corrupt (stream = 1, dts = 8467425232).
[mpegts @ 000002d5d73edbc0] Could not find codec parameters for stream 2 (Unknown: none ([151][0][0][0] / 0x0097)): unknown codec
Consider increasing the value for the 'analyzeduration' and 'probesize' options
[mpegts @ 000002d5d73edbc0] PES packet size mismatch
[mpegts @ 000002d5d73edbc0] Packet corrupt (stream = 1, dts = 8467425232).
Input #0, mpegts, from 'myfile.mpg':
  Duration: 00:30:00.63, start: 92282.982578, bitrate: 6249 kb/s
  Program 1
    Stream #0:0[0x1aab]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
    Stream #0:1[0x1abf]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, 5.1(side), fltp, 384 kb/s
    Stream #0:2[0x1ac1]: Unknown: none ([151][0][0][0] / 0x0097)
[mp4 @ 000002d5d7e90540] track 1: codec frame size is not set
Output #0, mp4, to 'myfile.trimmed.mp4':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 59.94 fps, 59.94 tbr, 90k tbn, 90k tbc
    Stream #0:1: Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, 5.1(side), fltp, 384 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (copy)
Press [q] to stop, [?] for help
frame= 9570 fps=0.0 q=-1.0 Lsize=  122587kB time=00:02:39.99 bitrate=6276.6kbits/s speed= 462x
video:114772kB audio:7545kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.220873%


  


  ffprobe -hide_banner myfile.trimmed.mp4
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'myfile.trimmed.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.45.100
  Duration: 00:02:40.96, start: 0.000000, bitrate: 6239 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv), 1280x720 [SAR 1:1 DAR 16:9], Closed Captions, 5890 kb/s, 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc (default)
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: ac3 (ac-3 / 0x332D6361), 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
    Side data:
      audio service type: main


  


  ...and i get the file that plays fine on a Mac, but not on Windows's default player.
The start time as reported by ffprobe is 0 (above), so that must've been cleaned up by either the trimming or the remuxing. When I look at frames, the first audio packet has a pkt_pts_time=0.000000, and the first video packet has a pkt_pts_time=0.452000.

  


  Where do I go next ?

  


• yet another screenshot encoding exercise with ffmpeg - stuck at getting AVFrame from ALT::CImage - VC++

  11 septembre 2013, par sith

  Total AV newbee here - trying to learn the ropes on using FFMpeg functions to encode movies. On searching for tutorials I found a few similar questions that I have linked here for reference :

  Encoding a screenshot into a video using FFMPEG

  [Libav-user] Encoding a screenshot into a video using FFMPEG

  Save bitmap to video (libavcodec ffmpeg)

  When converting from RGB to YUV using ffmpeg the video file the color is spread why ?

  How to convert RGB from YUV420p for ffmpeg encoder ?

  Encode bmp sequence with libavcodec...Help !

  Not able to encode image with ffmpeg

  For my setup FFMPEG is on VS12 - VC++ with MFC on win7.

  With the help of above samples, I am able to get "some" output from the encoder, but I am not sure in what format or state the output has been encoded. Neither VLC nor WMP can play this file. It does not even seem to recognize the metadata in the file to display the FPS or video length. What would normally cause that ? Also any pointers on what could be going wrong and how to approach fixing the problems would be great. [1]

  Here is the flow of my code :

  Step1 : capture desktop on to a CImg :

  int W=GetSystemMetrics(SM_CXSCREEN), H=GetSystemMetrics(SM_CYSCREEN), bpp=24; 
  
  CImage cImg; cImg.Create(W,H,bpp) 
  
  HDC hDC = cImg.GetDC(); 
  
  CWindowDC winDC(GetDesktopWindow()); 
  
  
  
  BitBlt(hDC, 0,0, rez.W(), rez.H(), winDC.m_hDC, 0, 0, SRCCOPY);

  At this point I am able to dump a screen shot into a bmp file -
  using cImg.Save( _T("test.bmp"), Gdiplus::ImageFormatBMP) ;

  Step2 : Extract the BMP bits from the CImg.

  HBITMAP hBitmap = (HBITMAP)cImg;
  
  HDC memDC = CreateCompatibleDC(NULL);
  
  SelectObject( memDC, hBitmap );
  
  
  
  BITMAPINFO bmi; // initialized bmi with {W,-H, plane=1, bitCount=24, comp=BI_RGB, size=W*H*3 }
  
  << removed bmi init code for conciseness. >>>
  
  
  
  BYTE *rgb24Data = new BYTE[W*H*3]; // 3 for 24bpp. 4 for 32...
  
  int ret = GetDIBits(memDC, hBitmap, 0, H, rgb24Data, &bmi, DIB_RGB_COLORS);

  At this point I faithfully believe rgb24Data points to pixel data :) - copied out of the cImg bitmap

  Step 3 : next I try to create an AV frame with the rgb24Data got from this CImg. Also this is where I have a massive knowledge gap. I am going to try and recover

  // setup the codecs and contexts here as per mohM's post
  
  
  
  AVCodec *currCodec = avcodec_find_encoder(CODEC_ID_MPEG4);
  
  
  
  AVCodecContext *codeCtxt = avcodec_alloc_context();  // init this with bate=400k, W, H,
  
  << removed codeCtxt init code for conciseness. >>>   //  time base 1/25, gop=10, max_b=1, fmt=YUV420
  
  
  
  avcodec_open(codeCtxt, currCodec);
  
  
  
  SwsContext *currSWSCtxt = sws_getContext( W, H, AV_PIX_FMT_RGB24, // FROM
  
                                            W, H, AV_PIX_FMT_YUV420P, // TO
  
                                            SWS_FAST_BILINEAR,
  
                                            NULL, NULL, NULL);
  
  
  
  // allocate and fill AVFrame
  
  int numBytes = avpicture_get_size(PIX_FMT_YUV420P, W, H);
  
  uint8_t *buffer=new uint8_t[numBytes];
  
  AVFrame *avFrame = avcodec_alloc_frame();
  
  avpicture_fill( (AVPicture*)avFrame, buffer, PIX_FMT_YUV420P, W, H );

  Step 4 : transform the data frame into YUV420P as we fill the frame.

  uint8_t * inData[1] = { rgb24Data };
  
  int inLinesize[1] = { 3*W }; // RGB stride
  
  sws_scale( currSWSCtxt, inData, inLinesize, 0, H,
  
             avFrame->data, avFrame->linesize);

  step 5 encode the frame and write out the output buffer into a file.

  int out_size = avcodec_encode_video( codeCtxt,
  
                                       outBuf,
  
                                       outBufSize,
  
                                       avFrame );
  
  
  
  fwrite(outBuf, 1, outBufSize, outFile );

  finally I close the file off with [0x00 0x00 0x01 0xb7]

  The first hint of things gone haywire is that for a 50 screens of 1920X1080 at 24bpp encoded at 25fps gives me a 507MB unplayable-mpeg file.

  As mentioned earlier, neither VLC nor WMP can play this file nor they even recognize the metadata in the file to display the FPS or video length. What would normally cause that ? Also any pointers on what could be going wrong and how to approach fixing the problems would be great. [2]

  Any guidance is much appreciated.