ffmpeg API h264 encoded video does not play on all platforms

问题

Edit: In the previous version I used a very old ffmpeg API. I now use the newest libraries. The problem has only changed slightly, from "Main" to "High".

I am using the ffmpeg C API to create a mp4 video in C++.

I want the resulting video to be of the profile "Constrained Baseline", so that the resulting video can be played on as much platforms as possible, especially mobile, but I get "High" profile every time, even though I hard coded the codec profile to be FF_PROFILE_H264_CONSTRAINED_BASELINE. As a result, the video does not play on all our testing platforms.

This is what "ffprobe video.mp4 -show_streams" tells about my video streams:

  Metadata:
major_brand     : isom
minor_version   : 512
compatible_brands: isomiso2avc1mp41
creation_time   : 1970-01-01 00:00:00
encoder         : Lavf53.5.0
  Duration: 00:00:13.20, start: 0.000000, bitrate: 553 kb/s
Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 320x180,
424 kb/s, 15 fps, 15 tbr, 15 tbn, 30 tbc
Metadata:
  creation_time   : 1970-01-01 00:00:00
  handler_name    : VideoHandler
Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 44100 Hz, stereo, s16, 12
kb/s
Metadata:
  creation_time   : 1970-01-01 00:00:00
  handler_name    : SoundHandler
-------VIDEO STREAM--------
[STREAM] 
index=0
codec_name=h264
codec_long_name=H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10

profile=High <-- This should be "Constrained Baseline"

codec_type=video
codec_time_base=1/30
codec_tag_string=avc1
codec_tag=0x31637661
width=320
height=180
has_b_frames=0
sample_aspect_ratio=N/A
display_aspect_ratio=N/A
pix_fmt=yuv420p
level=30
timecode=N/A
is_avc=1
nal_length_size=4
id=N/A
r_frame_rate=15/1
avg_frame_rate=15/1
time_base=1/15
start_time=0.000000
duration=13.200000
bit_rate=424252
nb_frames=198
nb_read_frames=N/A
nb_read_packets=N/A
TAG:creation_time=1970-01-01 00:00:00
TAG:language=und
TAG:handler_name=VideoHandler
[/STREAM]
-------AUDIO STREAM--------
[STREAM]
index=1
codec_name=aac
codec_long_name=Advanced Audio Coding
profile=unknown
codec_type=audio
codec_time_base=1/44100
codec_tag_string=mp4a
codec_tag=0x6134706d
sample_fmt=s16
sample_rate=44100
channels=2
bits_per_sample=0
id=N/A
r_frame_rate=0/0
avg_frame_rate=0/0
time_base=1/44100
start_time=0.000000
duration=13.165714
bit_rate=125301
nb_frames=567
nb_read_frames=N/A
nb_read_packets=N/A
TAG:creation_time=1970-01-01 00:00:00
TAG:language=und
TAG:handler_name=SoundHandler
[/STREAM]

This is the function I use to add a video stream. All the values that come from ptr-> are defined from outside, do those values have to be specific values to get the correct profile?:

static AVStream *add_video_stream( Cffmpeg_dll * ptr, AVFormatContext *oc, enum   CodecID codec_id )
{
AVCodecContext *c;
AVStream *st;  
AVCodec* codec;

// Get correct codec
codec = avcodec_find_encoder(codec_id);
if (!codec) {
    av_log(NULL, AV_LOG_ERROR, "%s","Video codec not found\n");
    exit(1);
}

// Create stream
st = avformat_new_stream(oc, codec);
if (!st) {
    av_log(NULL, AV_LOG_ERROR, "%s","Could not alloc stream\n");
    exit(1);
}

c = st->codec;

/* Get default values */
codec = avcodec_find_encoder(codec_id);
if (!codec) {
    av_log(NULL, AV_LOG_ERROR, "%s","Video codec not found (default values)\n");
    exit(1);
}
avcodec_get_context_defaults3(c, codec);

c->codec_id = codec_id;
c->codec_type = AVMEDIA_TYPE_VIDEO;

c->bit_rate = ptr->video_bit_rate;
av_log(NULL, AV_LOG_ERROR, " Bit rate: %i", c->bit_rate);

    c->qmin = ptr->qmin;
    c->qmax = ptr->qmax;
    c->me_method = ptr->me_method;
    c->me_subpel_quality = ptr->me_subpel_quality;
    c->i_quant_factor = ptr->i_quant_factor;
    c->qcompress = ptr->qcompress;
    c->max_qdiff = ptr->max_qdiff;

    // We need to set the level and profile to get videos that play (hopefully) on all platforms
    c->level = 30;
    c->profile = FF_PROFILE_H264_CONSTRAINED_BASELINE;

c->width = ptr->dstWidth; 
c->height = ptr->dstHeight; 

c->time_base.den = ptr->fps;
c->time_base.num = 1;
c->gop_size = ptr->fps;
c->pix_fmt = STREAM_PIX_FMT;
c->max_b_frames = 0;

// some formats want stream headers to be separate
if(oc->oformat->flags & AVFMT_GLOBALHEADER)
    c->flags |= CODEC_FLAG_GLOBAL_HEADER;

return st;
}

Additional info:

As a reference video, I use the gizmo.mp4 that Mozilla serves as an example that plays on every platform/browser. It definitely has the "Constrained Baseline" profile, and definitely works on all our testing smartphones. You can download it here. Our self-created video doesn't work on all platforms and I'm convinced this is because of the profile.

I am also using qt-faststart.exe to move the headers to the start of the file after creating the mp4, as this cannot be done in a good way in C++ directly. Could that be the problem?

Obviously, I am doing something wrong, but I don't know what it could be. I'd be thankful for every hint ;)

回答1:

I have the solution. After spending some time and discussions in the ffmpeg bug tracker and browsing for profile setting examples, I finally figured out the solution.

One needs to use av_opt_set(codecContext->priv_data, "profile", "baseline" (or any other desired profile), AV_OPT_SEARCH_CHILDREN)

So in my case that would be:

Wrong:

// We need to set the level and profile to get videos that play (hopefully) on all platforms
c->level = 30;
c->profile = FF_PROFILE_H264_CONSTRAINED_BASELINE;

Correct:

// Set profile to baseline
av_opt_set(c->priv_data, "profile", "baseline", AV_OPT_SEARCH_CHILDREN);

Completely unintuitive and contrary to the rest of the API usage, but that's ffmpeg philosophy. You don't need to understand it, you just need to understand how to use it ;)

来源：https://stackoverflow.com/questions/11537830/ffmpeg-api-h264-encoded-video-does-not-play-on-all-platforms

标签

encoding

ffmpeg

h.264

libavcodec