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  • FFMPEG : TS video copied to MP4, missing 3 first frames [closed]

    21 août 2023, par Vasilis Lemonidis

    Running :

    


    ffmpeg -i test.ts -fflags +genpts -c copy -y test.mp4


    


    for this test.ts, which has 30 frames, readable by opencv, I end up with 28 frames, out of which 27 are readable by opencv. More specifically :

    


    ffprobe -v error -select_streams v:0 -count_packets  -show_entries stream=nb_read_packets -of csv=p=0 tmp.ts 


    


    returns 30.

    


    ffprobe -v error -select_streams v:0 -count_packets     -show_entries stream=nb_read_packets -of csv=p=0 tmp.mp4


    


    returns 28.

    


    Using OpenCV in that manner

    


    cap = cv2.VideoCapture(tmp_path)
readMat = []
while cap.isOpened():
        ret, frame = cap.read()
        if not ret:
            break
        readMat.append(frame)


    


    I get for the ts file 30 frames, while for the mp4 27 frames.

    


    Could someone explain why the discrepancies ? I get no error during the transformation from ts to mp4 :

    


    ffmpeg version N-111746-gd53acf452f Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11.3.0 (GCC)
  configuration: --ld=g++ --bindir=/bin --extra-libs='-lpthread -lm' --pkg-config-flags=--static --enable-static --enable-gpl --enable-libaom --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libsvtav1 --enable-libdav1d --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --enable-cuda-nvcc --enable-cuvid --enable-nvenc --enable-libnpp 
  libavutil      58. 16.101 / 58. 16.101
  libavcodec     60. 23.100 / 60. 23.100
  libavformat    60. 10.100 / 60. 10.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 10.100 /  9. 10.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
  libpostproc    57.  2.100 / 57.  2.100
[mpegts @ 0x4237240] DTS discontinuity in stream 0: packet 5 with DTS 306003, packet 6 with DTS 396001
Input #0, mpegts, from 'tmp.ts':
  Duration: 00:00:21.33, start: 3.400000, bitrate: 15 kb/s
  Program 1 
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
  Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 300x300, 1 fps, 3 tbr, 90k tbn
Output #0, mp4, to 'test.mp4':
  Metadata:
    encoder         : Lavf60.10.100
  Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 300x300, q=2-31, 1 fps, 3 tbr, 90k tbn
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[out#0/mp4 @ 0x423e280] video:25kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 4.192123%
frame=   30 fps=0.0 q=-1.0 Lsize=      26kB time=00:00:21.00 bitrate=  10.3kbits/s speed=1e+04x 


    


    Additional information

    


    The origin of the video I am processing comes from a continuous stitching operation of still images ts videos, produced by this class update method :

    


    import cv2
import os
import subprocess
from tempfile import NamedTemporaryFile
class VideoUpdater:
    def __init__(
        self, video_path: str, framerate: int, timePerFrame: Optional[int] = None
    ):
        """
        Video updater takes in a video path, and updates it using a supplied frame, based on a given framerate.
        Args:
            video_path: str: Specify the path to the video file
            framerate: int: Set the frame rate of the video
        """
        if not video_path.endswith(".mp4"):
            LOGGER.warning(
                f"File type {os.path.splitext(video_path)[1]} not supported for streaming, switching to ts"
            )
            video_path = os.path.splitext(video_path)[0] + ".mp4"

        self._ps = None
        self.env = {
            
        }
        self.ffmpeg = "/usr/bin/ffmpeg "

        self.video_path = video_path
        self.ts_path = video_path.replace(".mp4", ".ts")
        self.tfile = None
        self.framerate = framerate
        self._video = None
        self.last_frame = None
        self.curr_frame = None


    def update(self, frame: np.ndarray):
        if len(frame.shape) == 2:
            frame = cv2.cvtColor(frame, cv2.COLOR_GRAY2BGR)
        else:
            frame = cv2.cvtColor(frame, cv2.COLOR_RGB2BGR)
        self.writeFrame(frame)

    def writeFrame(self, frame: np.ndarray):
        """
        The writeFrame function takes a frame and writes it to the video file.
        Args:
            frame: np.ndarray: Write the frame to a temporary file
        """


        tImLFrame = NamedTemporaryFile(suffix=".png")
        tVidLFrame = NamedTemporaryFile(suffix=".ts")

        cv2.imwrite(tImLFrame.name, frame)
        ps = subprocess.Popen(
            self.ffmpeg
            + rf"-loop 1 -r {self.framerate} -i {tImLFrame.name} -t {self.framerate} -vcodec libx264 -pix_fmt yuv420p -y {tVidLFrame.name}",
            env=self.env,
            shell=True,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        ps.communicate()
        if os.path.isfile(self.ts_path):
            # this does not work to watch, as timestamps are not updated
            ps = subprocess.Popen(
                self.ffmpeg
                + rf'-i "concat:{self.ts_path}|{tVidLFrame.name}" -c copy -y {self.ts_path.replace(".ts", ".bak.ts")}',
                env=self.env,
                shell=True,
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
            )
            ps.communicate()
            shutil.move(self.ts_path.replace(".ts", ".bak.ts"), self.ts_path)

        else:
            shutil.copyfile(tVidLFrame.name, self.ts_path)
        # fixing timestamps, we dont have to wait for this operation
        ps = subprocess.Popen(
            self.ffmpeg
            + rf"-i {self.ts_path} -fflags +genpts -c copy -y {self.video_path}",
            env=self.env,
            shell=True,
            # stdout=subprocess.PIPE,
            # stderr=subprocess.PIPE,
        )
        tImLFrame.close()
        tVidLFrame.close()


    


  • TS video copied to MP4, missing 3 first frames when programmatically read (ffmpeg bug)

    3 septembre 2023, par Vasilis Lemonidis

    Running :

    


    ffmpeg -i test.ts -fflags +genpts -c copy -y test.mp4


    


    for this test.ts, which has 30 frames, readable by opencv, I end up with 28 frames, out of which 27 are readable by opencv. More specifically :

    


    ffprobe -v error -select_streams v:0 -count_packets  -show_entries stream=nb_read_packets -of csv=p=0 tmp.ts 


    


    returns 30.

    


    ffprobe -v error -select_streams v:0 -count_packets     -show_entries stream=nb_read_packets -of csv=p=0 tmp.mp4


    


    returns 28.

    


    Using OpenCV in that manner

    


    cap = cv2.VideoCapture(tmp_path)
readMat = []
while cap.isOpened():
        ret, frame = cap.read()
        if not ret:
            break
        readMat.append(frame)


    


    I get for the ts file 30 frames, while for the mp4 27 frames.

    


    Could someone explain why the discrepancies ? I get no error during the transformation from ts to mp4 :

    


    ffmpeg version N-111746-gd53acf452f Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 11.3.0 (GCC)
  configuration: --ld=g++ --bindir=/bin --extra-libs='-lpthread -lm' --pkg-config-flags=--static --enable-static --enable-gpl --enable-libaom --enable-libass --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libsvtav1 --enable-libdav1d --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-nonfree --enable-cuda-nvcc --enable-cuvid --enable-nvenc --enable-libnpp 
  libavutil      58. 16.101 / 58. 16.101
  libavcodec     60. 23.100 / 60. 23.100
  libavformat    60. 10.100 / 60. 10.100
  libavdevice    60.  2.101 / 60.  2.101
  libavfilter     9. 10.100 /  9. 10.100
  libswscale      7.  3.100 /  7.  3.100
  libswresample   4. 11.100 /  4. 11.100
  libpostproc    57.  2.100 / 57.  2.100
[mpegts @ 0x4237240] DTS discontinuity in stream 0: packet 5 with DTS 306003, packet 6 with DTS 396001
Input #0, mpegts, from 'tmp.ts':
  Duration: 00:00:21.33, start: 3.400000, bitrate: 15 kb/s
  Program 1 
    Metadata:
      service_name    : Service01
      service_provider: FFmpeg
  Stream #0:0[0x100]: Video: h264 (High) ([27][0][0][0] / 0x001B), yuv420p(progressive), 300x300, 1 fps, 3 tbr, 90k tbn
Output #0, mp4, to 'test.mp4':
  Metadata:
    encoder         : Lavf60.10.100
  Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p(progressive), 300x300, q=2-31, 1 fps, 3 tbr, 90k tbn
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
[out#0/mp4 @ 0x423e280] video:25kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 4.192123%
frame=   30 fps=0.0 q=-1.0 Lsize=      26kB time=00:00:21.00 bitrate=  10.3kbits/s speed=1e+04x 


    


    Additional information

    


    The origin of the video I am processing comes from a continuous stitching operation of still images ts videos, produced by this class update method :

    


    import cv2
import os
import subprocess
from tempfile import NamedTemporaryFile
class VideoUpdater:
    def __init__(
        self, video_path: str, framerate: int, timePerFrame: Optional[int] = None
    ):
        """
        Video updater takes in a video path, and updates it using a supplied frame, based on a given framerate.
        Args:
            video_path: str: Specify the path to the video file
            framerate: int: Set the frame rate of the video
        """
        if not video_path.endswith(".mp4"):
            LOGGER.warning(
                f"File type {os.path.splitext(video_path)[1]} not supported for streaming, switching to ts"
            )
            video_path = os.path.splitext(video_path)[0] + ".mp4"

        self._ps = None
        self.env = {
            
        }
        self.ffmpeg = "/usr/bin/ffmpeg "

        self.video_path = video_path
        self.ts_path = video_path.replace(".mp4", ".ts")
        self.tfile = None
        self.framerate = framerate
        self._video = None
        self.last_frame = None
        self.curr_frame = None


    def update(self, frame: np.ndarray):
        if len(frame.shape) == 2:
            frame = cv2.cvtColor(frame, cv2.COLOR_GRAY2BGR)
        else:
            frame = cv2.cvtColor(frame, cv2.COLOR_RGB2BGR)
        self.writeFrame(frame)

    def writeFrame(self, frame: np.ndarray):
        """
        The writeFrame function takes a frame and writes it to the video file.
        Args:
            frame: np.ndarray: Write the frame to a temporary file
        """


        tImLFrame = NamedTemporaryFile(suffix=".png")
        tVidLFrame = NamedTemporaryFile(suffix=".ts")

        cv2.imwrite(tImLFrame.name, frame)
        ps = subprocess.Popen(
            self.ffmpeg
            + rf"-loop 1 -r {self.framerate} -i {tImLFrame.name} -t {self.framerate} -vcodec libx264 -pix_fmt yuv420p -y {tVidLFrame.name}",
            env=self.env,
            shell=True,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        ps.communicate()
        if os.path.isfile(self.ts_path):
            # this does not work to watch, as timestamps are not updated
            ps = subprocess.Popen(
                self.ffmpeg
                + rf'-i "concat:{self.ts_path}|{tVidLFrame.name}" -c copy -y {self.ts_path.replace(".ts", ".bak.ts")}',
                env=self.env,
                shell=True,
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
            )
            ps.communicate()
            shutil.move(self.ts_path.replace(".ts", ".bak.ts"), self.ts_path)

        else:
            shutil.copyfile(tVidLFrame.name, self.ts_path)
        # fixing timestamps, we dont have to wait for this operation
        ps = subprocess.Popen(
            self.ffmpeg
            + rf"-i {self.ts_path} -fflags +genpts -c copy -y {self.video_path}",
            env=self.env,
            shell=True,
            # stdout=subprocess.PIPE,
            # stderr=subprocess.PIPE,
        )
        tImLFrame.close()
        tVidLFrame.close()


    


  • FFmpeg library is detecting pixel format of VP9 video stream not correctly

    6 avril 2023, par Pikachu

    I am using a C code to detect pixel format of VP9 video stream in a WebM container. FFmpeg version 6.0, full shared library build, downloaded from official website. Operating system is Windows 10. I feed the library with a VP9 video encoded with alpha channel, pixel format is YUVA420p. It detects pixel format as YUV420p.

    


    I have found a similar question on StackOverflow.com, Is there a way to force FFMPEG to decode a video stream with alpha from ​a WebM video encoded with libvpx-vp9 ?, but it does not actually help.

    


    When I override the decoder with a libvpx, it continues to detect the pixel format as YUV420p instead of YUVA420p.

    


    C code is following. Note that error handling in code is omitted here for StackOverflow question to be shorter.

    


    AVFormatContext *fmt_ctx = NULL;
int err = avformat_open_input(&fmt_ctx, infp, NULL, NULL);
err = avformat_find_stream_info(fmt_ctx, NULL);
int stream = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);
AVCodecParameters *codecpar = fmt_ctx->streams[stream]->codecpar;

const AVCodec *codec = NULL;
if (codecpar->codec_id == AV_CODEC_ID_VP9) {
    codec = avcodec_find_decoder_by_name(CODEC_LIBVPX_VP9);
} else {
    codec = avcodec_find_decoder(codecpar->codec_id);
}

AVCodecContext *ctx = avcodec_alloc_context3(codec);
err = avcodec_parameters_to_context(ctx, codecpar);
av_log(NULL, AV_LOG_DEBUG, "Pixel format: %d.\n", ctx->pix_fmt); //TODO:DEBUG.
err = avcodec_open2(ctx, codec, NULL);


    


    The program tells Pixel format: 0., which means AV_PIX_FMT_YUV420P, not the AV_PIX_FMT_YUVA420P !

    


    If I override pixel format manually, I am able to decode video with alpha channel and to see the transparent background, but it breaks the logics, because when a real YUV420p pixel format comes in and gets overridden by YUVA420p, this will be a problem.

    


    if (codecpar->codec_id == AV_CODEC_ID_VP9) {
    if (strcmp(codec->name, CODEC_LIBVPX_VP9) == 0) {
        if (ctx->pix_fmt == AV_PIX_FMT_YUV420P) {
            ctx->pix_fmt = AV_PIX_FMT_YUVA420P;
        }
    }
}


    


    At the same time ffmpeg tool started from command line with libvpx decoder tells that my video has YUVA420p pixel format. Output is following.

    


    D:\Temp\4>ffmpeg -c:v libvpx-vp9 -i yuva.webm
ffmpeg version 6.0-full_build-www.gyan.dev Copyright (c) 2000-2023 the FFmpeg developers
  built with gcc 12.2.0 (Rev10, Built by MSYS2 project)
  configuration: --enable-gpl --enable-version3 --enable-shared --disable-w32threads --disable-autodetect --enable-fontconfig --enable-iconv --enable-gnutls --enable-libxml2 --enable-gmp --enable-bzlib --enable-lzma --enable-libsnappy --enable-zlib --enable-librist --enable-libsrt --enable-libssh --enable-libzmq --enable-avisynth --enable-libbluray --enable-libcaca --enable-sdl2 --enable-libaribb24 --enable-libdav1d --enable-libdavs2 --enable-libuavs3d --enable-libzvbi --enable-librav1e --enable-libsvtav1 --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs2 --enable-libxvid --enable-libaom --enable-libjxl --enable-libopenjpeg --enable-libvpx --enable-mediafoundation --enable-libass --enable-frei0r --enable-libfreetype --enable-libfribidi --enable-liblensfun --enable-libvidstab --enable-libvmaf --enable-libzimg --enable-amf --enable-cuda-llvm --enable-cuvid --enable-ffnvcodec --enable-nvdec --enable-nvenc --enable-d3d11va --enable-dxva2 --enable-libvpl --enable-libshaderc --enable-vulkan --enable-libplacebo --enable-opencl --enable-libcdio --enable-libgme --enable-libmodplug --enable-libopenmpt --enable-libopencore-amrwb --enable-libmp3lame --enable-libshine --enable-libtheora --enable-libtwolame --enable-libvo-amrwbenc --enable-libilbc --enable-libgsm --enable-libopencore-amrnb --enable-libopus --enable-libspeex --enable-libvorbis --enable-ladspa --enable-libbs2b --enable-libflite --enable-libmysofa --enable-librubberband --enable-libsoxr --enable-chromaprint
  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
[libvpx-vp9 @ 000001ecdf6002c0] v1.13.0-71-g45dc0d34d
    Last message repeated 1 times
Input #0, matroska,webm, from 'yuva.webm':
  Metadata:
    ENCODER         : Lavf60.3.100
  Duration: 00:00:05.55, start: 0.000000, bitrate: 227 kb/s
  Stream #0:0: Video: vp9 (Profile 0), yuva420p(tv, progressive), 1920x1080, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 1k tbn
    Metadata:
      alpha_mode      : 1
      ENCODER         : Lavc60.3.100 libvpx-vp9
      DURATION        : 00:00:05.550000000
At least one output file must be specified


    


    Here is my YUVA420p in the first video stream at the end of the console output :

    


    Stream #0:0: Video: vp9 (Profile 0), yuva420p(tv, progressive), 1920x1080, SAR 1:1 DAR 16:9, 60 fps, 60 tbr, 1k tbn


    


    


    The questions are following.

    


      

    1. How to detect real pixel format of VP9 video with FFmpeg library in C code reliably ?

      2. 


    2. Why is the C code not detecting the actual pixel format even with codec overriden to libvpx ?

      3. 


    


    Thank you.

    


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