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• FFMpeg Mobile video encoding stutter

  15 février 2014, par Sammaye

  I have been playing around with ffmpeg and video encoding and even though my mp4's work great on desktop, they are smooth etc they are terrible on mobile devices. They stutter and load very slowly and I am trying to figure out the problem.

  As an example I made a page using the media element plugin : http://mediaelementjs.com/ and on it I first placed the video that comes with mediaelementjs and it worked well, it scaled to desktop and mobile and loaded quickly and played without any stutter.

  However I loaded my video and it was slow and full of stutter, but only on mobile. So I thought it might be S3 (where it is hosted) but saved the file locally and same thing.

  I am hoping someone who knows h.264 and/or ffmpeg can point me in the direction of why ; here is the current command I am running on ffmpeg :

  ffmpeg -i $input_file_name -vcodec libx264 -r 100 -bt 300k -ac 2 -ar 48000 -ab 192k -strict -2 -y $output_temp_file 2>&1

  So what have I missed ?

• How to record the bluetooth audio from my phone in my pc using ffmpeg ?

  12 septembre 2023, par Juan Inzunza

  I have my phone connected via Bluetooth to my PC and playing audio in my phone so i can hear that audio in my pc and i was trying to record that audio in my PC using ffmpeg this is the command i got so far

  


  ffmpeg -f pulse -ac 1 -ar 44100 -i alsa_input.usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00.mono-fallback -f pulse -ac 2 -ar 44100 -i bluez_source.84_5F_04_75_B9_F6.a2dp_source -filter_complex amix=inputs=2 -i /dev/video5 -s 640x480 -vcodec libx264 -preset veryfast -crf 18 -acodec libmp3lame -ar 44100 -q:a 1 -pix_fmt yuv420p -aq 0 ~/Videos


  


  "bluez_source.84_5F_04_75_B9_F6.a2dp_source" is the name of the bluetooth audio source (my phone) but the problem is, if i am not playing audio on the device, just disappears when i execute this command "pactl list sources", and appears again when i play audio, so is listed when i run "pactl list sources" and i have to keep the phone playing audio so ffmpeg recognizes that device and not fail when executed.

  


  Finally my question is how can i keep that device in running state or suspended state without need to play audio all the time.

  


  gandalf@Mordor:~$ pactl list sources
Source #64
    State: IDLE
    Name: alsa_output.usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00.analog-stereo.monitor
    Description: Monitor of KT USB Audio Analog Stereo
    Driver: module-alsa-card.c
    Sample Specification: s16le 2ch 44100Hz
    Channel Map: front-left,front-right
    Owner Module: 85
    Mute: no
    Volume: front-left: 65536 / 100% / 0.00 dB,   front-right: 65536 / 100% / 0.00 dB
            balance 0.00
    Base Volume: 65536 / 100% / 0.00 dB
    Monitor of Sink: alsa_output.usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00.analog-stereo
    Latency: 0 usec, configured 2000000 usec
    Flags: DECIBEL_VOLUME LATENCY 
    Properties:
        device.description = "Monitor of KT USB Audio Analog Stereo"
        device.class = "monitor"
        alsa.card = "1"
        alsa.card_name = "KT USB Audio"
        alsa.long_card_name = "KTMicro KT USB Audio at usb-0000:03:00.3-3, full speed"
        alsa.driver_name = "snd_usb_audio"
        device.bus_path = "pci-0000:03:00.3-usb-0:3:1.0"
        sysfs.path = "/devices/pci0000:00/0000:00:08.1/0000:03:00.3/usb1/1-3/1-3:1.0/sound/card1"
        udev.id = "usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00"
        device.bus = "usb"
        device.vendor.id = "12d1"
        device.vendor.name = "Huawei Technologies Co., Ltd."
        device.product.id = "0010"
        device.product.name = "KT USB Audio"
        device.serial = "KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000-"
        device.string = "1"
        module-udev-detect.discovered = "1"
        device.icon_name = "audio-card-usb"
    Formats:
        pcm

Source #65
    State: SUSPENDED
    Name: alsa_input.usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00.mono-fallback
    Description: KT USB Audio Mono
    Driver: module-alsa-card.c
    Sample Specification: s16le 1ch 44100Hz
    Channel Map: mono
    Owner Module: 85
    Mute: no
    Volume: mono: 65536 / 100% / 0.00 dB
            balance 0.00
    Base Volume: 65536 / 100% / 0.00 dB
    Monitor of Sink: n/a
    Latency: 0 usec, configured 0 usec
    Flags: HARDWARE HW_MUTE_CTRL HW_VOLUME_CTRL DECIBEL_VOLUME LATENCY 
    Properties:
        alsa.resolution_bits = "16"
        device.api = "alsa"
        device.class = "sound"
        alsa.class = "generic"
        alsa.subclass = "generic-mix"
        alsa.name = "USB Audio"
        alsa.id = "USB Audio"
        alsa.subdevice = "0"
        alsa.subdevice_name = "subdevice #0"
        alsa.device = "0"
        alsa.card = "1"
        alsa.card_name = "KT USB Audio"
        alsa.long_card_name = "KTMicro KT USB Audio at usb-0000:03:00.3-3, full speed"
        alsa.driver_name = "snd_usb_audio"
        device.bus_path = "pci-0000:03:00.3-usb-0:3:1.0"
        sysfs.path = "/devices/pci0000:00/0000:00:08.1/0000:03:00.3/usb1/1-3/1-3:1.0/sound/card1"
        udev.id = "usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00"
        device.bus = "usb"
        device.vendor.id = "12d1"
        device.vendor.name = "Huawei Technologies Co., Ltd."
        device.product.id = "0010"
        device.product.name = "KT USB Audio"
        device.serial = "KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000-"
        device.string = "hw:1"
        device.buffering.buffer_size = "176400"
        device.buffering.fragment_size = "88200"
        device.access_mode = "mmap+timer"
        device.profile.name = "mono-fallback"
        device.profile.description = "Mono"
        device.description = "KT USB Audio Mono"
        module-udev-detect.discovered = "1"
        device.icon_name = "audio-card-usb"
    Ports:
        analog-input-mic: Microphone (type: Mic, priority: 8700, availability unknown)
    Active Port: analog-input-mic
    Formats:
        pcm

Source #68
    State: RUNNING
    Name: bluez_source.84_5F_04_75_B9_F6.a2dp_source
    Description: Juan's S20 FE
    Driver: module-bluez5-device.c
    Sample Specification: s16le 2ch 44100Hz
    Channel Map: front-left,front-right
    Owner Module: 23
    Mute: no
    Volume: front-left: 53151 /  81% / -5.46 dB,   front-right: 53151 /  81% / -5.46 dB
            balance 0.00
    Base Volume: 65536 / 100% / 0.00 dB
    Monitor of Sink: n/a
    Latency: 68928 usec, configured 68537 usec
    Flags: HARDWARE DECIBEL_VOLUME LATENCY 
    Properties:
        bluetooth.protocol = "a2dp_source"
        bluetooth.codec = "sbc"
        device.description = "Juan's S20 FE"
        device.string = "84:5F:04:75:B9:F6"
        device.api = "bluez"
        device.class = "sound"
        device.bus = "bluetooth"
        device.form_factor = "phone"
        bluez.path = "/org/bluez/hci0/dev_84_5F_04_75_B9_F6"
        bluez.class = "0x5a020c"
        bluez.alias = "Juan's S20 FE"
        device.icon_name = "audio-card-bluetooth"
    Ports:
        phone-input: Phone (type: Phone, priority: 0, available)
    Active Port: phone-input
    Formats:
        pcm


  


  This is the error i am getting when there's no playing audio in my phone.

  


  ffmpeg version 4.4.2-0ubuntu0.22.04.1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
  configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 70.100 / 56. 70.100
  libavcodec     58.134.100 / 58.134.100
  libavformat    58. 76.100 / 58. 76.100
  libavdevice    58. 13.100 / 58. 13.100
  libavfilter     7.110.100 /  7.110.100
  libswscale      5.  9.100 /  5.  9.100
  libswresample   3.  9.100 /  3.  9.100
  libpostproc    55.  9.100 / 55.  9.100
Guessed Channel Layout for Input Stream #0.0 : mono
Input #0, pulse, from 'alsa_input.usb-KTMicro_KT_USB_Audio_2021-06-25-0000-0000-0000--00.mono-fallback':
  Duration: N/A, start: 1694557964.268337, bitrate: 705 kb/s
  Stream #0:0: Audio: pcm_s16le, 44100 Hz, mono, s16, 705 kb/s
bluez_source.84_5F_04_75_B9_F6.a2dp_source: Input/output error



  


• What's FFmpeg doing with avcodec_send_packet() ?

  4 avril, par Jim

  I'm trying to optimise a piece of software for playing video, which internally uses the FFmpeg libraries for decoding. We've found that on some large (4K, 60fps) video, it sometimes takes longer to decode a frame than that frame should be displayed for ; sadly, because of the problem domain, simply buffering/skipping frames is not an option.

  


  However, it appears that the FFmpeg executable is able to decode the video in question fine, at about 2x speed, so I've been trying to work out what we're doing wrong.

  


  I've written a very stripped-back decoder program for testing ; the source is here (it's about 200 lines). From profiling it, it appears that the one major bottleneck during decoding is the avcodec_send_packet() function, which can take up to 50ms per call. However, measuring the same call in FFmpeg shows strange behaviour :

  


  

  


  (these are the times taken for each call to avcodec_send_packet() in milliseconds, when decoding a 4K 25fps VP9-encoded video.)

  


  Basically, it seems that when FFmpeg uses this function, it only really takes any amount of time to complete every N calls, where N is the number of threads being used for decoding. However, both my test decoder and the actual product use 4 threads for decoding, and this doesn't happen ; when using frame-based threading, the test decoder behaves like FFmpeg using only 1 thread. This would seem to indicate that we're not using multithreading at all, but we've still seen performance improvements by using more threads.

  


  FFmpeg's results average out to being about twice as fast overall as our decoders, so clearly we're doing something wrong. I've been reading through FFmpeg's source to try to find any clues, but it's so far eluded me.

  


  My question is : what's FFmpeg doing here that we're not ? Alternatively, how can we increase the performance of our decoder ?

  


  Any help is greatly appreciated.