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Sur d’autres sites (4910)

  • latency when streaming x264

    18 novembre 2013, par tobsen

    I would like to produce a zerolatency live video stream and play it in VLC player with as little latency as possible.

    This are the settings I currently use :

    x264_param_default_preset( &m_Params, "veryfast", "zerolatency" );
    

    
m_Params.i_threads              =   2;
    
m_Params.b_sliced_threads       =   true;
    
m_Params.i_width                =   m_SourceWidth;
    
m_Params.i_height               =   m_SourceHeight;
    

    
m_Params.b_intra_refresh        =   1;
    

    
m_Params.b_vfr_input            =   true;
    
m_Params.i_timebase_num         =   1;
    
m_Params.i_timebase_den         =   1000;
    

    
m_Params.i_fps_num              =   1;
    
m_Params.i_fps_den              =   60;
    

    
m_Params.rc.i_vbv_max_bitrate   =   512;
    
m_Params.rc.i_vbv_buffer_size   =   256;
    
m_Params.rc.f_vbv_buffer_init   =   1.1f;
    

    
m_Params.rc.i_rc_method         =   X264_RC_CRF;
    
m_Params.rc.f_rf_constant       =   24;
    
m_Params.rc.f_rf_constant_max   =   35;
    

    
m_Params.b_annexb               =   0;
    
m_Params.b_repeat_headers       =   0;
    
m_Params.b_aud                  =   0;
    

    
x264_param_apply_profile( &m_Params, "high" );

    Using those settings, I have the following issues :

    • VLC shows lots of missing frames (see screenshot, "verloren"). I am not sure if this is an issue.
    • If I set a value <200ms for the network stream delay in VLC, VLC renders a few frames and than stops to decode/render frames.
    • If I set a value >= 200ms for the network stream delay in VLC, everything looks good so far but the latency is, obviously, 200ms, which is too high.

    Question :
    Which settings (x264lib and VLC) should I use in order to encode and stream with as little latency as possible ?

    enter image description here

  • FFmpeg encoding produces slightly incompatible MKV/MP4 container

    11 juin 2018, par james2048

    I’ve been using the FFmpeg libraries to read and write media files using the C API.

    So far, reading seems to be pretty straightforward. I am able to read frames which I can then process, convert to RGB, process, and then convert back to YUV420 to be encoded.

    The encoded files play back with VLC media player fine, and Windows Media Player if I have a codec pack installed. However, they do behave strangely : the stock Windows 10 player won’t play them, same for Adobe Premiere. Also thumbnailers don’t work on it.
    Basically it seems like nothing other than VLC or FFmpeg itself can play/process the file. I have seen this with both MP4 and MKV, so it is not a format-specific issue.

    The problems go away once you remux the file with FFmpeg, for example "ffmpeg -i input.mkv -c copy output.mkv". Everything can play the file correctly.
    Also, the "remuxing.c" sample from the official samples works as well, with the same library version and compilers that I’m using (Visual Studio 2017, FFmpeg compiled with MinGW). It will fix the file and make it playable in all software.

    I’m not sure what could be causing this. I also don’t understand what the remuxing "fixed". It must be a container issue as the frames aren’t touched by remuxing.
    I have analysed the output MKVs with FFprobe -show_packets. It seems to have budged the packet timestamps a little constant factor, and the output stream now has
    is_avc=true and nal_length_size=4 instead of is_avc=false and nal_length_size=0, but apart from that the files are identical.

    Now here’s the output of FFprobe with the 3 last test packets, stream info and format info for both streams. As you can see, they are identical except for a couple of field. But something in here must have been "fixed" during remuxing to make it work.

    [PACKET]
    
codec_type=video
    
stream_index=0
    
pts=59050
    
pts_time=59.050000
    
dts=58890
    
dts_time=58.890000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=427
    
pos=277358
    
flags=__
    
[/PACKET]
    
[PACKET]
    
codec_type=video
    
stream_index=0
    
pts=58970
    
pts_time=58.970000
    
dts=58970
    
dts_time=58.970000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=205
    
pos=277792
    
flags=__
    
[/PACKET]
    
[PACKET]
    
codec_type=video
    
stream_index=0
    
pts=59130
    
pts_time=59.130000
    
dts=59050
    
dts_time=59.050000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=268
    
pos=278004
    
flags=__
    
[/PACKET]
    
[STREAM]
    
index=0
    
codec_name=h264
    
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
    
profile=Main
    
codec_type=video
    
codec_time_base=1/2000
    
codec_tag_string=[0][0][0][0]
    
codec_tag=0x0000
    
width=720
    
height=576
    
coded_width=720
    
coded_height=576
    
has_b_frames=2
    
sample_aspect_ratio=N/A
    
display_aspect_ratio=N/A
    
pix_fmt=yuv420p
    
level=50
    
color_range=unknown
    
color_space=unknown
    
color_transfer=unknown
    
color_primaries=unknown
    
chroma_location=left
    
field_order=progressive
    
timecode=N/A
    
refs=1
    
is_avc=false
    
nal_length_size=0
    
id=N/A
    
r_frame_rate=299/12
    
avg_frame_rate=1000/1
    
time_base=1/1000
    
start_pts=0
    
start_time=0.000000
    
duration_ts=N/A
    
duration=N/A
    
bit_rate=N/A
    
max_bit_rate=N/A
    
bits_per_raw_sample=8
    
nb_frames=N/A
    
nb_read_frames=N/A
    
nb_read_packets=737
    
DISPOSITION:default=1
    
DISPOSITION:dub=0
    
DISPOSITION:original=0
    
DISPOSITION:comment=0
    
DISPOSITION:lyrics=0
    
DISPOSITION:karaoke=0
    
DISPOSITION:forced=0
    
DISPOSITION:hearing_impaired=0
    
DISPOSITION:visual_impaired=0
    
DISPOSITION:clean_effects=0
    
DISPOSITION:attached_pic=0
    
DISPOSITION:timed_thumbnails=0
    
TAG:DURATION=00:00:59.211000000
    
[/STREAM]
    
[FORMAT]
    
filename=testEncLeft.mkv
    
nb_streams=1
    
nb_programs=0
    
format_name=matroska,webm
    
format_long_name=Matroska / WebM
    
start_time=0.000000
    
duration=59.211000
    
size=278349
    
bit_rate=37607
    
probe_score=100
    
TAG:COMMENT=Slickline Player Export
    
TAG:ENCODER=Lavf57.83.100
    
[/FORMAT]

    And the info after remuxing, which works :

    [PACKET]
    
codec_type=video
    
stream_index=0
    
pts=59050
    
pts_time=59.050000
    
dts=58890
    
dts_time=58.890000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=427
    
pos=277418
    
flags=__
    
[/PACKET]
    
[PACKET]
    
codec_type=video
    
stream_index=0
    
pts=58970
    
pts_time=58.970000
    
dts=58970
    
dts_time=58.970000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=205
    
pos=277852
    
flags=__
    
[/PACKET]
    
[PACKET]
    
codec_type=video
    
stream_index=0
    
pts=59130
    
pts_time=59.130000
    
dts=59050
    
dts_time=59.050000
    
duration=1
    
duration_time=0.001000
    
convergence_duration=N/A
    
convergence_duration_time=N/A
    
size=268
    
pos=278064
    
flags=__
    
[/PACKET]
    
[STREAM]
    
index=0
    
codec_name=h264
    
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
    
profile=Main
    
codec_type=video
    
codec_time_base=1/2000
    
codec_tag_string=[0][0][0][0]
    
codec_tag=0x0000
    
width=720
    
height=576
    
coded_width=720
    
coded_height=576
    
has_b_frames=2
    
sample_aspect_ratio=N/A
    
display_aspect_ratio=N/A
    
pix_fmt=yuv420p
    
level=50
    
color_range=unknown
    
color_space=unknown
    
color_transfer=unknown
    
color_primaries=unknown
    
chroma_location=left
    
field_order=progressive
    
timecode=N/A
    
refs=1
    
is_avc=true
    
nal_length_size=4
    
id=N/A
    
r_frame_rate=299/12
    
avg_frame_rate=1000/1
    
time_base=1/1000
    
start_pts=0
    
start_time=0.000000
    
duration_ts=N/A
    
duration=N/A
    
bit_rate=N/A
    
max_bit_rate=N/A
    
bits_per_raw_sample=8
    
nb_frames=N/A
    
nb_read_frames=N/A
    
nb_read_packets=737
    
DISPOSITION:default=1
    
DISPOSITION:dub=0
    
DISPOSITION:original=0
    
DISPOSITION:comment=0
    
DISPOSITION:lyrics=0
    
DISPOSITION:karaoke=0
    
DISPOSITION:forced=0
    
DISPOSITION:hearing_impaired=0
    
DISPOSITION:visual_impaired=0
    
DISPOSITION:clean_effects=0
    
DISPOSITION:attached_pic=0
    
DISPOSITION:timed_thumbnails=0
    
TAG:DURATION=00:00:59.212000000
    
[/STREAM]
    
[FORMAT]
    
filename=fixedLeft.mkv
    
nb_streams=1
    
nb_programs=0
    
format_name=matroska,webm
    
format_long_name=Matroska / WebM
    
start_time=0.000000
    
duration=59.212000
    
size=278409
    
bit_rate=37615
    
probe_score=100
    
TAG:COMMENT=Slickline Player Export
    
TAG:ENCODER=Lavf58.12.100
    
[/FORMAT]

    Here is how I’m setting up the output context, for reference : it’s pretty standard, following the sample code.

    int ret;
    

    
avformat_alloc_output_context2(&amp;outputFormatCtx, nullptr, nullptr, outFilePath.c_str());
    

    
av_dict_set(&amp;outputFormatCtx->metadata, "comment", "FFmpeg Export", 0);
    

    
if (!outputFormatCtx)
    
{
    
    LOG_AND_THROW("Could not allocate output context");
    
}
    

    
outputVideoStream = avformat_new_stream(outputFormatCtx, nullptr);
    
outputVideoStream->time_base = AVRational{ 1, AV_TIME_BASE }; // Stream timebase will be used by codec
    

    
if (!outputVideoStream)
    
{
    
    LOG_AND_THROW("Failed allocating output stream");
    
}
    

    
// defaults to "libx264"
    
AVCodec *outCodec = avcodec_find_encoder_by_name(selectedCodecName.c_str());
    

    
if (!outCodec)
    
{
    
    LOG_AND_THROW("Failed finding output codec");
    
}
    

    
AVDictionary *opts = nullptr;
    

    
if (selectedCodecName == "libx264")
    
{
    
    opts = getX264CodecOptions();
    
}
    

    
encoderCtx = avcodec_alloc_context3(outCodec);
    

    
if (!encoderCtx)
    
{
    
    LOG_AND_THROW("Failed to allocate the encoder context");
    
}
    

    
encoderCtx->width = width;
    
encoderCtx->height = height;
    
encoderCtx->pix_fmt = AV_PIX_FMT_YUV420P;
    
// time base for the frames we will provide to the encoder
    
encoderCtx->time_base = AVRational{ 1, AV_TIME_BASE };
    
// convert framerate from double to rational
    
encoderCtx->framerate = AVRational{ (int)(frameRate * AV_TIME_BASE), AV_TIME_BASE};
    

    
// Match encoderCtx time base for the stream
    
outputVideoStream->time_base = encoderCtx->time_base;
    

    
ret = avcodec_open2(encoderCtx, outCodec, &amp;opts);
    

    
if (ret &lt; 0)
    
{
    
    LOG_AND_THROW_PARAM("Cannot open video encoder for stream: %d", ret);
    
}
    

    
// Fill in some params for MP4 stream, details about encoder
    
ret = avcodec_parameters_from_context(outputVideoStream->codecpar, encoderCtx);
    

    
if (ret &lt; 0)
    
{
    
    LOG_AND_THROW_PARAM("Failed to copy encoder parameters to output stream: %d", ret);
    
}
    

    
if (outputFormatCtx->oformat->flags &amp; AVFMT_GLOBALHEADER)
    
{
    
    encoderCtx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
    
}
    

    
av_dump_format(outputFormatCtx, 0, filePath.c_str(), 1);
    

    
// End of encoder settings, setting up MP4
    
if (!(outputFormatCtx->oformat->flags &amp; AVFMT_NOFILE))
    
{
    
    ret = avio_open(&amp;outputFormatCtx->pb, outFilePath.c_str(), AVIO_FLAG_WRITE);
    

    
    if (ret &lt; 0)
    
    {
    
        LOG_AND_THROW_PARAMSTR("Could not open output file '%s'", outFilePath.c_str());
    
    }
    
}
    

    
ret = avformat_write_header(outputFormatCtx, nullptr);
    

    
if (ret &lt; 0)
    
{
    
    LOG_AND_THROW_PARAM("Error occurred when opening output file for writing: %d", ret);
    
}

    Can anyone help me figure out why the container is not playing properly ?

    Thanks in advance.

    -James

  • How to add network caching to ffmpeg

    10 novembre 2018, par JohnnyF

    I have a network with random latency of 200-400ms per msg

    when i use VLC i add this command to the reciever node

    --network-caching=1000

    this adds 1 sec delay on the receiver, that fixes the problem with the network random delays

    how can i do it in FFMPEG (google finds only solutions of LOW delays)

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