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• Is there an efficient way to retrieve frames from a video in Android ?

  28 mars 2015, par Naveed

  I have an app which requires me to retrieve frames from a video and do some processing with them. However it seems like that the frame retrieval is very slow to the point where it is unacceptable. Sometimes it is taking upto 2.5 second to retrieve a single frame. I am using the MediaMetadataRetriever as most stackoverflow questions suggested. However the performance is very bad. Here is what I have :

     private List<bitmap> retrieveFrames() {
  
  
  
          MediaMetadataRetriever fmmr = new MediaMetadataRetriever();
  
          fmmr.setDataSource("/path/to/some/video.mp4");
  
          String strLength = fmmr.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
  
          long milliSecs = Long.parseLong(strLength);
  
          long microSecLength = milliSecs * 1000;
  
  
  
          Log.d("TAG", "length: " + microSecLength);
  
          long one_sec = 1000000; // one sec in micro seconds
  
  
  
          ArrayList<bitmap> frames = new ArrayList&lt;>();
  
          int j = 0;
  
          for (int i = 0; i &lt; microSecLength; i += (one_sec / 5)) {
  
              long time = System.currentTimeMillis();
  
              Bitmap frame = fmmr.getFrameAtTime(i, MediaMetadataRetriever.OPTION_CLOSEST);
  
              j++;
  
              Log.d("TAG", "Frame number: " + j + " Time taken: " + (System.currentTimeMillis() - time));
  
              // commented out because each frame would be written to disk instead of holding them in memory
  
              //  frames.add(frame);
  
          }
  
          fmmr.release();
  
          return frames;
  
      }
  
  </bitmap></bitmap>

  The above will logs :

  03-26 21:49:29.781  13213-13239/com.example.naveed.myapplication D/TAG﹕ length: 4949000
  
  03-26 21:49:30.187  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 1 Time taken: 406
  
  03-26 21:49:30.779  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 2 Time taken: 592
  
  03-26 21:49:31.578  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 3 Time taken: 799
  
  03-26 21:49:32.632  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 4 Time taken: 1054
  
  03-26 21:49:33.895  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 5 Time taken: 1262
  
  03-26 21:49:35.382  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 6 Time taken: 1486
  
  03-26 21:49:37.128  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 7 Time taken: 1746
  
  03-26 21:49:39.077  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 8 Time taken: 1948
  
  03-26 21:49:41.287  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 9 Time taken: 2210
  
  03-26 21:49:43.717  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 10 Time taken: 2429
  
  03-26 21:49:44.093  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 11 Time taken: 376
  
  03-26 21:49:44.707  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 12 Time taken: 614
  
  03-26 21:49:45.539  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 13 Time taken: 831
  
  03-26 21:49:46.597  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 14 Time taken: 1057
  
  03-26 21:49:47.875  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 15 Time taken: 1278
  
  03-26 21:49:49.384  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 16 Time taken: 1508
  
  03-26 21:49:51.112  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 17 Time taken: 1728
  
  03-26 21:49:53.096  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 18 Time taken: 1983
  
  03-26 21:49:55.315  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 19 Time taken: 2218
  
  03-26 21:49:57.711  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 20 Time taken: 2396
  
  03-26 21:49:58.065  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 21 Time taken: 354
  
  03-26 21:49:58.640  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 22 Time taken: 574
  
  03-26 21:49:59.369  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 23 Time taken: 728
  
  03-26 21:50:00.112  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 24 Time taken: 742
  
  03-26 21:50:00.834  13213-13239/com.example.naveed.myapplication D/TAG﹕ Frame number: 25 Time taken: 721

  As you can see from above, it is taking about 18 - 25 sec to retrieve 25 frames from a 4 sec long video.

  I have also tried this which uses FFmpeg underneath to do the same. I am not sure how well this library is implemented but it only improves the over all performance by a couple of seconds meaning it takes about 15-20 sec to do the same.

  So my question is : is there a way to do it quicker ? My friend has an iOS app where he does something similar but it only takes couple of seconds and he is grabbing even more frames however he is not sure how to do it on android.

  Is there anything on android that would speed up the process. Am I approaching this wrong ?

  The end goal is to stitch those frames together into a gif.

• Split h.264 stream into multiple parts in python

  31 janvier 2023, par BillPlayz

  My objective is to split an h.264 stream into multiple parts, meaning while reading the stream from a pipe i would like to save it into x second long packages (in my case 10).

  


  I am using a libcamera-vid subprocess on my Raspberry Pi that outputs the h.264 stream into stdout.
  
Might be irrelevant, depends : libcamera-vid outputs a message every frame and I am able to locate it at isFrameStopLine
To convert the stream, I use an ffmpeg subprocess, as you can see in the code below.

  


  Imagine it like that :
  
Stream is running...
  
- Start recording to a file
  
- Sleep x seconds
  
- Finish recording to file
  
- Start recording a new file
  
- Sleep x seconds
  
- Finish recording the new file
  
- and so on...

  


  Here is my current code, however upon running the first export succeeds, and after the second or third the ffmpeg-subprocess is terminating with the error :
  
pipe:: Invalid data found when processing input
  
And shortly after, the python process, because of the ffmpeg termination i believe.
Traceback (most recent call last):   File "/home/survpi-camera/main.py", line 56, in <module>     processStreamLine(readData)   File "/home/survpi-camera/main.py", line 16, in processStreamLine     streamInfo["process"].stdin.write(data) BrokenPipeError: [Errno 32] Broken pipe</module>

  


  recentStreamProcesses = []
streamInfo = {
    "lastStreamStart": -1,
    "process": None
}

def processStreamLine(data):
    isInfoLine = ((data.startswith(b"[") and (b"INFO" in data)) or (data == b"Preview window unavailable"))
    isFrameStopLine = (data.startswith(b"#") and (b" fps) exp" in data))
    if ((not isInfoLine) and (not isFrameStopLine)):
        streamInfo["process"].stdin.write(data)
    
    if (isFrameStopLine):
        if (time.time() - streamInfo["lastStreamStart"] >= 10):
            print("10 seconds passed, exporting...")
            exportStream()
            createNewStream()

def createNewStream():
    streamInfo["lastStreamStart"] = time.time()
    streamInfo["process"] = subprocess.Popen([
        "ffmpeg",
        "-r","30",
        "-i","-",
        "-c","copy",("/home/survpi-camera/" + str(round(time.time())) + ".mp4")
    ],stdin=subprocess.PIPE,stderr=subprocess.STDOUT)
    print("Created new streamProcess.")

def exportStream():
    print("Exporting...")
    streamInfo["process"].stdin.close()
    recentStreamProcesses.append(streamInfo["process"])


cameraProcess = subprocess.Popen([
    "libcamera-vid",
    "-t","0",
    "--width","1920",
    "--height","1080",
    "--codec","h264",
    "--inline",
    "--listen",
    "-o","-"
],stdout=subprocess.PIPE,stdin=subprocess.PIPE,stderr=subprocess.STDOUT)

createNewStream()

while True:
    readData = cameraProcess.stdout.readline()
    
    processStreamLine(readData)


  


  Thank you in advance !

  


• ffmpeg hwo to choose the best bit rate for HLS streaming ?

  7 février 2023, par Josef Kranz

  I'm building a video streaming white label product, but I've run into the following scenario where I'm not sure what might be the optimal way to get the best video quality in return. At the moment I'm using crf based encoding, which is from a streaming based point of view a very bad idea. From a quality point of view, it will definitely give me the best quality and also the best efficiency. Why is crf based encoding bad for streaming ? First you have a non-fixed file size, meaning your bit rate might vary between 20 kbps and 20 Mbit/s depending on the codec and picture motion of the current frames ...
When you have such heavily varying stream according to the bit rate, automatic quality selection at the player might not function correctly, and the player automatically switches from 1080p to 480p for no reason (using VideoJS here).

  


  To fix this issue, it's fine if I set minrate, maxrate with ffmpeg but this will also come at the cost that some frames might look pixelated, which I absolutely do not want.

  


  Currently, my encoding command looks something like this :

  


  /usr/bin/ffmpeg -i "/tmp/VODProcessing/Tester 2160p UHD-HDR.mp4" -map 0:0 -c:v libsvtav1 -crf 19 -vf zscale=width=3840:height=2160 -svtav1-params "profile=0:enable-force-key-frames=1:superres-mode=1:enable-tf=0:tune=0:enable-overlays=1:scd=1:scm=2:enable-mfmv=1:enable-cdef=1:enable-dlf=1:fast-decode=1:color-primaries=9:transfer-characteristics=16:matrix-coefficients=9:input-depth=10:mastering-display=G(0.265,0.69)B(0.15,0.06)R(0.68,0.32)WP(0.3127,0.329)L(4000.0,0.005):content-light=368,226:enable-hdr=1:color-range=1" -pix_fmt yuv420p10le -color_trc smpte2084 -color_primaries bt2020 -colorspace bt2020nc -chroma_sample_location:v topleft -color_range:v pc -max_muxing_queue_size 1024 -preset 7 -bf 0 -force_key_frames "expr:gte(t,n_forced*4.004)" -keyint_min 48 -sc_threshold 0 -use_timeline 1 -use_template 1 -map_metadata -1 -map_chapters -1 -f hls -seg_duration 4.004 -hls_time 4.004 -streaming 1 -hls_list_size 0 -hls_segment_filename "/tmp/VODProcessing/output/Tester 2160p UHD-HDR/v-av01-2160p-av01.0.12M.10_PQ/f-%04d.m4s"  -hls_fmp4_init_filename "init-v-av01-2160p-av01.0.12M.10_PQ.m4s"  -hls_segment_type fmp4 -hls_playlist_type vod -movflags frag_keyframe+frag_every_frame+write_colr+prefer_icc+skip_trailer+faststart -hls_flags independent_segments -strict experimental "/tmp/VODProcessing/output/Tester 2160p UHD-HDR/v-av01-2160p-av01.0.12M.10_PQ/master.m3u8"


  


  Which will form a stream made out of independent m4s segments. As you can see, I'm using libsvtav1 in crf mode to output the result in AV1.

  


  Now my question is, how can I have the same nice quality output as with the crf mode while having a static/fixed bit rate ? Will 2 pass encoding solve this problem by distributing the pixels or data rate differently ?

  


  Thanks in advance