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• Why isnt the dpi argument increasing resolution in matplotlib ?

  18 décembre 2023, par BananaBusters

  Ive been making little videos of the Lorenz attractor recently by plotting various steps in the Lorenz attractor trace in python, saving the plots as images then combining the images into a video. By default, a saved plot in python doesnt really have good resolution so I have been trying to boost the resolution by using the 'dpi=' argument in plt.savefig, but recently the resolution hasnt been increasing and has been staying the default value for some videos, but for others it comes out crisp and clear. Can anyone tell me where im going wrong ? Here is the code im using along with a youtube link showing the low resolution even after using a high dpi argument. And no, its not just youtube compressing the video, it looked like that before uploading as well.

  


  Youtube video showing problem : https://www.youtube.com/watch?v=0TpxeMxYs5A

  


  Code :

  


  # lorenzAttractorTrace() takes in the amount of frames you want to video to be along with the system paramters s, r and b. Default value is just a known value that gives a known result to use as sanity checks
# Will save images to target directory where you will then have to run ffmpeg through the command line to use. Ffmpeg comand is given in the next line
# ffmpeg -start_number 0 -framerate 60 -i graph%01d.png video.webm

def lorenzAttractorTrace(frames, s=10, r=28, b=2.667, clean=False, rotation=False):
    #Empty the target directory
    clearDirectory()

    #Calculate the array of points according to the lorenz system
    #Do this outside the main loop so that we only calculate it once rather than a bazillion times and annihilate memory
    dt = 0.01
    numSteps = frames

    xyzs = np.empty((numSteps+1, 3))  # Need one more for the initial values
    xyzs[0] = (0., 1., 1.05)  # Set initial values
    for i in range(numSteps):
        xyzs[i + 1] = xyzs[i] + lorenz(xyzs[i],s,r,b) * dt

    # Checking if the attractor is clean or not to determine what the first frame should look like     
    if clean == True:
        #plot the first frame outside of the main loop, same idea as initial conditions just with a frame
        ax = plt.figure().add_subplot(projection='3d')
        ax.plot(*xyzs[0].T, lw=0.5)
        ax.set_xlabel("X Axis")
        ax.set_ylabel("Y Axis")
        ax.set_zlabel("Z Axis")
        ax.grid(None)
        ax.axis('off')
        plt.savefig('./Images for simulation/graph'+str(0)+'.png')
        plt.close('all')
    else:
        #plot the first frame outside of the main loop, same idea as initial conditions just with a frame
        ax = plt.figure().add_subplot(projection='3d')
        ax.plot(*xyzs[0].T, lw=0.5)
        ax.set_xlabel("X Axis")
        ax.set_ylabel("Y Axis")
        ax.set_zlabel("Z Axis")
        ax.set_title("Lorenz Attractor")
        plt.savefig('./Images for simulation/graph'+str(0)+'.png')
        plt.close('all')
    
    #Non-rotation video
    if rotation == False:
        #Initialize frame to 1 so that our indexing for xyzs in the main loop prints from 0-frame. If frame was 0 then we would be plotting xysz from xyzs[0] ot xyzs[0] which we cant do. We need atleast xyzs[0] to xyzs[1]
        frame = 1
        while frame < numSteps:
            ax = plt.figure().add_subplot(projection='3d')
            ax.plot(*xyzs[:frame].T, lw=0.5) #Recall this [:frame] notion means we plot the array from xyzs[0] to xyzs[frame]
            ax.set_xlabel("X Axis")
            ax.set_ylabel("Y Axis")
            ax.set_zlabel("Z Axis")
            plt.xlim((-25,25))
            plt.ylim((-30,35))
            ax.set_zlim(0,60)
            if clean == True:
                ax.grid(None)
                ax.axis('off')
            else:
                ax.set_title("Lorenz Attractor")
                pass
            plt.savefig('./Images for simulation/graph'+str(frame)+'.png', dpi=300) # dpi argument increases resolution
            plt.close('all')
            frame = frame + 1
    #Rotation video, add in the ax.view_init() function which takes in spherical coordinate
    else:
        #Initialize frame to 1 so that our indexing for xyzs in the main loop prints from 0-frame. If frame was 0 then we would be plotting xysz from xyzs[0] ot xyzs[0] which we cant do. We need atleast xyzs[0] to xyzs[1]
        frame = 1
        angle = 0
        while frame < numSteps:
            ax = plt.figure().add_subplot(projection='3d')
            ax.plot(*xyzs[:frame].T, lw=0.5) #Recall this [:frame] notion means we plot the array from xyzs[0] to xyzs[frame]
            ax.set_xlabel("X Axis")
            ax.set_ylabel("Y Axis")
            ax.set_zlabel("Z Axis")
            plt.xlim((-25,25))
            plt.ylim((-30,35))
            ax.set_zlim(0,60)
            ax.view_init(30,angle)
            if clean == True:
                ax.grid(None)
                ax.axis('off')
            else:
                ax.set_title("Lorenz Attractor")
                pass
            plt.savefig('./Images for simulation/graph'+str(frame)+'.png', dpi=300) # dpi argument increases resolution
            plt.close('all')
            frame = frame + 1
            angle = angle + 1


  


• How to update this script to generate HLS video with different resolution streams ? [closed]

  1er décembre 2023, par Andy Z

  I have the following FFmpeg script :

  


  ffmpeg -i video.mp4 -i video.vtt \
 -map 0:v -map 0:a:0 -map 1 \
 -s:v:0 1080x1920 -c:v:0 h264 -b:v:0 500K \
 -c:a:0 copy -c:a:1 copy -c:a:2 copy -c:s webvtt \
 -f hls -hls_playlist_type vod -var_stream_map "v:0,a:0,s:0" \
 -master_pl_name video.m3u8 -hls_time 6 -hls_list_size 0 -hls_allow_cache 1 -start_number 1 \
 -hls_segment_filename "output/hls/%v/seg-%d.ts" output/hls/%v/index.m3u8


  


  Currently it only produces one 1080x1920 stream, how do I produce more lower resolution ones so it can adjust based on client bandwidth ?

  


  Also, I've noticed that it doesn't add the reference to the VTT file to the master HLS playlist ; I had to add this manually but is there a way to make FFmpeg do it for me ?

  


  #EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",CHARACTERISTICS="public.accessibility.transcribes-spoken-dialog",URI="0/index_vtt.m3u8"


  


  I've tried this, but I get an argument error :

  


  ffmpeg -i video.mp4 -i video.vtt \
 -map 0:v -map 0:a:0 -map 1 \
 -s:v:0 1080x1920 -c:v:0 h264 -b:v:0 500K \
 -s:v:1 720x1280 -c:v:1 h264 -b:v:1 300K \
 -s:v:2 480x854 -c:v:2 h264 -b:v:2 150K \
 -c:a:0 copy -c:a:1 copy -c:a:2 copy -c:s webvtt \
 -f hls -hls_playlist_type vod -var_stream_map "v:0,a:0,s:0 v:1,a:1 s:1 v:2,a:2 s:2" \
 -master_pl_name video.m3u8 -hls_time 6 -hls_list_size 0 -hls_allow_cache 1 -start_number 1 \
 -hls_segment_filename "output/hls/%v/seg-%d.ts" output/hls/%v/index.m3u8


  


• FFMPEG concat 2 files of different resolution hangs

  6 octobre 2023, par knagode

  I am trying to concat 2 videos of different size and resize it to 426x240 :

  


  ffmpeg -y -i video_1.mp4 -i video_2.mp4 -filter_complex '[0]scale=426:240:force_original_aspect_ratio=decrease,pad=426:240:(ow-iw)/2:(oh-ih)/2,setsar=1[v0];[1]scale=426:240:force_original_aspect_ratio=decrease,pad=426:240:(ow-iw)/2:(oh-ih)/2,setsar=1[v1];[v0][0:a:0][v1][1:a:0]concat=n=2:v=1:a=1[v][a]' -map '[v]' -map '[a]' concatenated_video.mp4


  


  In the output I see :

  


  ffmpeg version 6.0 Copyright (c) 2000-2023 the FFmpeg developers
  built with Apple clang version 14.0.3 (clang-1403.0.22.14.1)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/6.0_1 --enable-shared --enable-pthreads --enable-version3 --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libaribb24 --enable-libbluray --enable-libdav1d --enable-libjxl --enable-libmp3lame --enable-libopus --enable-librav1e --enable-librist --enable-librubberband --enable-libsnappy --enable-libsrt --enable-libsvtav1 --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvmaf --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-libspeex --enable-libsoxr --enable-libzmq --enable-libzimg --disable-libjack --disable-indev=jack --enable-videotoolbox --enable-audiotoolbox
  libavutil      58.  2.100 / 58.  2.100
  libavcodec     60.  3.100 / 60.  3.100
  libavformat    60.  3.100 / 60.  3.100
  libavdevice    60.  1.100 / 60.  1.100
  libavfilter     9.  3.100 /  9.  3.100
  libswscale      7.  1.100 /  7.  1.100
  libswresample   4. 10.100 /  4. 10.100
  libpostproc    57.  1.100 / 57.  1.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video_1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:05.76, start: 0.000000, bitrate: 1582 kb/s
  Stream #0:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 640x360 [SAR 1:1 DAR 16:9], 1473 kb/s, 30 fps, 30 tbr, 15360 tbn (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc. Created on: 08/17/2020.
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264
  Stream #0:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 112 kb/s (default)
    Metadata:
      handler_name    : ISO Media file produced by Google Inc. Created on: 08/17/2020.
      vendor_id       : [0][0][0][0]
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video_2.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Duration: 00:00:16.40, start: 0.000000, bitrate: 383 kb/s
  Stream #1:0[0x1](und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709, progressive), 426x240 [SAR 640:639 DAR 16:9], 245 kb/s, 29.97 fps, 29.97 tbr, 30k tbn (default)
    Metadata:
      handler_name    : Core Media Video
      vendor_id       : [0][0][0][0]
      encoder         : Lavc60.3.100 libx264
  Stream #1:1[0x2](eng): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s (default)
    Metadata:
      handler_name    : Core Media Audio
      vendor_id       : [0][0][0][0]
Stream mapping:
  Stream #0:0 (h264) -> scale:default
  Stream #0:1 (aac) -> concat
  Stream #1:0 (h264) -> scale:default
  Stream #1:1 (aac) -> concat
  concat -> Stream #0:0 (libx264)
  concat -> Stream #0:1 (aac)
Press [q] to stop, [?] for help
[vost#0:0/libx264 @ 0x7fc777006280] Frame rate very high for a muxer not efficiently supporting it.
Please consider specifying a lower framerate, a different muxer or setting vsync/fps_mode to vfr
[libx264 @ 0x7fc777006580] using SAR=1/1
[libx264 @ 0x7fc777006580] MB rate (405000000) > level limit (16711680)
[libx264 @ 0x7fc777006580] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x7fc777006580] profile High, level 6.2, 4:2:0, 8-bit
[libx264 @ 0x7fc777006580] 264 - core 164 r3095 baee400 - H.264/MPEG-4 AVC codec - Copyleft 2003-2022 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 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=7 lookahead_threads=1 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=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'concatenated_video.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf60.3.100
  Stream #0:0: Video: h264 (avc1 / 0x31637661), yuv420p(tv, progressive), 426x240 [SAR 1:1 DAR 71:40], q=2-31, 1000k tbn
    Metadata:
      encoder         : Lavc60.3.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: N/A
  Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc60.3.100 aac
[vost#0:0/libx264 @ 0x7fc777006280] More than 1000 frames duplicated  1.1kbits/s speed=4.94x


  


  Process hangs and I see that ffmpeg uses 500% of the CPU. Any idea how to fix (deal with) this ?

  


  I can open both videos on my computer and play them.