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• ffmpeg : handle videos with changing resolution

  5 mars 2021, par mSourire

  I write a program, which concatenates input list of videos programmatically. The problem is that these videos are parts of a recorded stream, and their resolution may change few times within the same file.
Currently, if that happens, ffmpeg fails, saying that it's not possible to concat files with different resolutions. Is there a way to make ffmpeg handling this automatically ? A good solution would be selective scaling of frames with unexpected resolution.

  


  Here is a listing :

  


  ffmpeg -y -i 1.mkv -i 1.mka
-max_muxing_queue_size 10000
-preset veryfast -r 30 -crf 20 -b:a 96000 -vbr on
-strict experimental
-filter_complex '
color=black:s=320x240:d=7ms[black0];
aevalsrc=0:d=15ms[silence1];
[black0][0]concat=n=2:v=1:a=0[video];
[1][silence1]concat=n=2:v=0:a=1[audio]'
-map [video] -map [audio] -c:v libvpx -c:a libopus output.webm

ffmpeg version 4.3.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with Apple clang version 11.0.0 (clang-1100.0.33.17)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.3.1_9 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libdav1d --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100
Input #0, matroska,webm, from '1.mkv':
  Metadata:
    encoder         : GStreamer matroskamux version 1.8.1.1
    creation_time   : 2021-03-02T13:44:03.000000Z
  Duration: 00:01:48.41, start: 0.710000, bitrate: 757 kb/s
    Stream #0:0(eng): Video: vp8, yuv420p(progressive), 320x240, SAR 1:1 DAR 4:3, 120 tbr, 1k tbn, 1k tbc (default)
    Metadata:
      title           : Video
Input #1, matroska,webm, from '1.mka':
  Metadata:
    encoder         : GStreamer matroskamux version 1.8.1.1
    creation_time   : 2021-03-02T13:44:03.000000Z
  Duration: 00:01:48.40, start: 0.703000, bitrate: 38 kb/s
    Stream #1:0(eng): Audio: opus, 48000 Hz, stereo, fltp (default)
    Metadata:
      title           : Audio
Codec AVOption preset (Configuration preset) specified for output file #0 (output.webm) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Stream mapping:
  Stream #0:0 (vp8) -> concat:in1:v0
  Stream #1:0 (opus) -> concat:in0:a0
  concat -> Stream #0:0 (libvpx)
  concat -> Stream #0:1 (libopus)
Press [q] to stop, [?] for help
[libvpx @ 0x7fe08a80bc00] v1.9.0
[libvpx @ 0x7fe08a80bc00] Bitrate not specified for constrained quality mode, using default of 256kbit/sec
Output #0, webm, to 'output.webm':
  Metadata:
    encoder         : Lavf58.45.100
    Stream #0:0: Video: vp8 (libvpx), yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=-1--1, 256 kb/s, 30 fps, 1k tbn, 30 tbc (default)
    Metadata:
      encoder         : Lavc58.91.100 libvpx
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
    Stream #0:1: Audio: opus (libopus), 48000 Hz, stereo, flt, 96 kb/s (default)
    Metadata:
      encoder         : Lavc58.91.100 libopus
[Parsed_color_0 @ 0x7fe089815940] EOF timestamp not reliable
[Parsed_concat_2 @ 0x7fe088501980] Input link in0:v0 parameters (size 640x480, SAR 1:1) do not match the corresponding output link in0:v0 parameters (320x240, SAR 1:1)
[Parsed_concat_2 @ 0x7fe088501980] Failed to configure output pad on Parsed_concat_2
Error reinitializing filters!
Failed to inject frame into filter network: Invalid argument
Error while processing the decoded data for stream #0:0
[libopus @ 0x7fe08a810c00] 1 frames left in the queue on closing
Conversion failed!


  


  Here is the only such video with "floating" resolution, which cannot be concatenated with 320x240 color filter.

  


• FFmpeg - Convert video changing resolution and bitrates

  8 avril 2021, par parvares

  I’m trying to convert a video and change these parameters :

  


  resolution : from 1.280x720 to 640x360 pixels

  


  average bitrate : from 1.410 to 300 kb/s

  


  maximum bitrate : from 1.680 to 2500 kb/s

  


  Sampling rate : from 48.0 to 44.1 kHz

  


  Bit rate audio : 128 kb/s

  


  I used this string with ffmpeg vers. 4.3.2-2021-02-20 full build :

  


  ffmpeg -i input.mp4 -c:v -vf scale=640:360 libx264 -b:v 300k -maxrate 2500k -bufsize 2500k -crf 25 -c:a -ar 44100 libfdk_aac -b:a 128k output.mp4


  


  I get the error : “ffmpeg unable to find a suitable output format for scale ‘640:360’ scale 640:360 : invalid argument”. Could you help me please ?

  


  Below is the original file analyzed by MediaInfo, thanks !

  


  General

  


  Complete name : C :\Users\parvares\Desktop\input.mp4
Format : MPEG-4
Format profile : Base Media
Codec ID : isom (isom/iso2/avc1/mp41)
File size : 424 MiB
Duration : 38 min 21 s
Overall bit rate : 1 545 kb/s
Writing application : Lavf58.64.100

  


  Video

  


  ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L3.1
Format settings : CABAC / 4 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 4 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 38 min 21 s
Bit rate : 1 410 kb/s
Maximum bit rate : 1 680 kb/s
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 25.000 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.061
Stream size : 387 MiB (91%)
Writing library : x264 core 161 r3027 4121277
Encoding settings : cabac=1 / ref=2 / deblock=1:0:0 / analyse=0x3:0x113 / me=hex / subme=6 / 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=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=1 / keyint=250 / keyint_min=125 / scenecut=40 / intra_refresh=0 / rc_lookahead=125 / rc=crf / mbtree=1 / crf=20.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / vbv_maxrate=1680 / vbv_bufsize=8400 / crf_max=0.0 / nal_hrd=none / filler=0 / ip_ratio=1.40 / aq=1:1.00
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Codec configuration box : avcC

  


  Audio

  


  ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 38 min 21 s
Bit rate mode : Constant
Bit rate : 129 kb/s
Channel(s) : 2 channels
Channel layout : L R
Sampling rate : 48.0 kHz
Frame rate : 46.875 FPS (1024 SPF)
Compression mode : Lossy
Stream size : 35.3 MiB (8%)
Default : Yes
Alternate group : 1

  


• avcodec_decode_video2 fails to decode after frame resolution change

  10 avril 2021, par Krzysztof Kansy

  I'm using ffmpeg in Android project via JNI to decode real-time H264 video stream. On the Java side I'm only sending the the byte arrays into native module. Native code is running a loop and checking data buffers for new data to decode. Each data chunk is processed with :
  

  



  int bytesLeft = data->GetSize();
int paserLength = 0;
int decodeDataLength = 0;
int gotPicture = 0;
const uint8_t* buffer = data->GetData();
while (bytesLeft > 0) {
    AVPacket packet;
    av_init_packet(&packet);
    paserLength = av_parser_parse2(_codecPaser, _codecCtx, &packet.data, &packet.size, buffer, bytesLeft, AV_NOPTS_VALUE, AV_NOPTS_VALUE, AV_NOPTS_VALUE);
    bytesLeft -= paserLength;
    buffer += paserLength;

    if (packet.size > 0) {
        decodeDataLength = avcodec_decode_video2(_codecCtx, _frame, &gotPicture, &packet);
    }
    else {
        break;
    }
    av_free_packet(&packet);
}

if (gotPicture) {
// pass the frame to rendering
}


  



  The system works pretty well until incoming video's resolution changes. I need to handle transition between 4:3 and 16:9 aspect ratios. While having AVCodecContext configured as follows :

  



  _codecCtx->flags2|=CODEC_FLAG2_FAST;
_codecCtx->thread_count = 2;
_codecCtx->thread_type = FF_THREAD_FRAME;

if(_codec->capabilities&CODEC_FLAG_LOW_DELAY){
    _codecCtx->flags|=CODEC_FLAG_LOW_DELAY;
}


  



  I wasn't able to continue decoding new frames after video resolution change. The got_picture_ptr flag that avcodec_decode_video2 enables when whole frame is available was never true after that.
  
This ticket made me wonder if the issue isn't connected with multithreading. Only useful thing I've noticed is that when I change thread_type to FF_THREAD_SLICE the decoder is not always blocked after resolution change, about half of my attempts were successfull. Switching to single-threaded processing is not possible, I need more computing power. Setting up the context to one thread does not solve the problem and makes the decoder not keeping up with processing incoming data.
  
Everything work well after app restart.
  

  



  I can only think of one workoround (it doesn't really solve the problem) : unloading and loading the whole library after stream resolution change (e.g as mentioned in here). I don't think it's good tho, it will propably introduce other bugs and take a lot of time (from user's viewpoint).

  



  Is it possible to fix this issue ?

  



  EDIT :
  
I've dumped the stream data that is passed to decoding pipeline. I've changed the resolution few times while stream was being captured. Playing it with ffplay showed that in moment when resolution changed and preview in application froze, ffplay managed to continue, but preview is glitchy for a second or so. You can see full ffplay log here. In this case video preview stopped when I changed resolution to 960x720 for the second time. (Reinit context to 960x720, pix_fmt: yuv420p in log).