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ijkplayer框架简析 -- avcodec_open2
source link: http://yydcdut.com/2019/03/03/ijkplayer-ffmpeg-avcodec-open2/?amp%3Butm_medium=referral
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avcodec_open2()
主要作用是初始化一个视音频编解码器的 AVCodecContext
avcodec_open2
int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *codec, AVDictionary **options)
{
int ret = 0;
AVDictionary *tmp = NULL;
const AVPixFmtDescriptor *pixdesc;
if (avcodec_is_open(avctx))
return 0;
if ((!codec && !avctx->codec)) {
av_log(avctx, AV_LOG_ERROR, "No codec provided to avcodec_open2()\n");
return AVERROR(EINVAL);
}
if ((codec && avctx->codec && codec != avctx->codec)) {
av_log(avctx, AV_LOG_ERROR, "This AVCodecContext was allocated for %s, "
"but %s passed to avcodec_open2()\n", avctx->codec->name, codec->name);
return AVERROR(EINVAL);
}
if (!codec)
codec = avctx->codec;
if (avctx->extradata_size < 0 || avctx->extradata_size >= FF_MAX_EXTRADATA_SIZE)
return AVERROR(EINVAL);
if (options)
av_dict_copy(&tmp, *options, 0);
ret = ff_lock_avcodec(avctx, codec);
if (ret < 0)
return ret;
avctx->internal = av_mallocz(sizeof(AVCodecInternal));
if (!avctx->internal) {
ret = AVERROR(ENOMEM);
goto end;
}
avctx->internal->pool = av_mallocz(sizeof(*avctx->internal->pool));
if (!avctx->internal->pool) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->to_free = av_frame_alloc();
if (!avctx->internal->to_free) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->compat_decode_frame = av_frame_alloc();
if (!avctx->internal->compat_decode_frame) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->buffer_frame = av_frame_alloc();
if (!avctx->internal->buffer_frame) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->buffer_pkt = av_packet_alloc();
if (!avctx->internal->buffer_pkt) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->ds.in_pkt = av_packet_alloc();
if (!avctx->internal->ds.in_pkt) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->last_pkt_props = av_packet_alloc();
if (!avctx->internal->last_pkt_props) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
avctx->internal->skip_samples_multiplier = 1;
if (codec->priv_data_size > 0) {
if (!avctx->priv_data) {
avctx->priv_data = av_mallocz(codec->priv_data_size);
if (!avctx->priv_data) {
ret = AVERROR(ENOMEM);
goto end;
}
if (codec->priv_class) {
*(const AVClass **)avctx->priv_data = codec->priv_class;
av_opt_set_defaults(avctx->priv_data);
}
}
if (codec->priv_class && (ret = av_opt_set_dict(avctx->priv_data, &tmp)) < 0)
goto free_and_end;
} else {
avctx->priv_data = NULL;
}
// 将输入的 AVDictionary 形式的选项设置到 AVCodecContext
if ((ret = av_opt_set_dict(avctx, &tmp)) < 0)
goto free_and_end;
if (avctx->codec_whitelist && av_match_list(codec->name, avctx->codec_whitelist, ',') <= 0) {
av_log(avctx, AV_LOG_ERROR, "Codec (%s) not on whitelist \'%s\'\n", codec->name, avctx->codec_whitelist);
ret = AVERROR(EINVAL);
goto free_and_end;
}
// only call ff_set_dimensions() for non H.264/VP6F/DXV codecs so as not to overwrite previously setup dimensions
if (!(avctx->coded_width && avctx->coded_height && avctx->width && avctx->height &&
(avctx->codec_id == AV_CODEC_ID_H264 || avctx->codec_id == AV_CODEC_ID_VP6F || avctx->codec_id == AV_CODEC_ID_DXV))) {
if (avctx->coded_width && avctx->coded_height)
ret = ff_set_dimensions(avctx, avctx->coded_width, avctx->coded_height);
else if (avctx->width && avctx->height)
ret = ff_set_dimensions(avctx, avctx->width, avctx->height);
if (ret < 0)
goto free_and_end;
}
// 检查宽和高
if ((avctx->coded_width || avctx->coded_height || avctx->width || avctx->height)
&& ( av_image_check_size2(avctx->coded_width, avctx->coded_height, avctx->max_pixels, AV_PIX_FMT_NONE, 0, avctx) < 0
|| av_image_check_size2(avctx->width, avctx->height, avctx->max_pixels, AV_PIX_FMT_NONE, 0, avctx) < 0)) {
av_log(avctx, AV_LOG_WARNING, "Ignoring invalid width/height values\n");
ff_set_dimensions(avctx, 0, 0);
}
// 检查宽高比
if (avctx->width > 0 && avctx->height > 0) {
if (av_image_check_sar(avctx->width, avctx->height,
avctx->sample_aspect_ratio) < 0) {
av_log(avctx, AV_LOG_WARNING, "ignoring invalid SAR: %u/%u\n",
avctx->sample_aspect_ratio.num,
avctx->sample_aspect_ratio.den);
avctx->sample_aspect_ratio = (AVRational){ 0, 1 };
}
}
/* if the decoder init function was already called previously,
* free the already allocated subtitle_header before overwriting it */
if (av_codec_is_decoder(codec))
av_freep(&avctx->subtitle_header);
if (avctx->channels > FF_SANE_NB_CHANNELS) {
ret = AVERROR(EINVAL);
goto free_and_end;
}
avctx->codec = codec;
if ((avctx->codec_type == AVMEDIA_TYPE_UNKNOWN || avctx->codec_type == codec->type) &&
avctx->codec_id == AV_CODEC_ID_NONE) {
avctx->codec_type = codec->type;
avctx->codec_id = codec->id;
}
if (avctx->codec_id != codec->id || (avctx->codec_type != codec->type
&& avctx->codec_type != AVMEDIA_TYPE_ATTACHMENT)) {
av_log(avctx, AV_LOG_ERROR, "Codec type or id mismatches\n");
ret = AVERROR(EINVAL);
goto free_and_end;
}
avctx->frame_number = 0;
avctx->codec_descriptor = avcodec_descriptor_get(avctx->codec_id);
// 检查编码器是否出于“实验”阶段
if ((avctx->codec->capabilities & AV_CODEC_CAP_EXPERIMENTAL) &&
avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {
const char *codec_string = av_codec_is_encoder(codec) ? "encoder" : "decoder";
AVCodec *codec2;
av_log(avctx, AV_LOG_ERROR,
"The %s '%s' is experimental but experimental codecs are not enabled, "
"add '-strict %d' if you want to use it.\n",
codec_string, codec->name, FF_COMPLIANCE_EXPERIMENTAL);
codec2 = av_codec_is_encoder(codec) ? avcodec_find_encoder(codec->id) : avcodec_find_decoder(codec->id);
if (!(codec2->capabilities & AV_CODEC_CAP_EXPERIMENTAL))
av_log(avctx, AV_LOG_ERROR, "Alternatively use the non experimental %s '%s'.\n",
codec_string, codec2->name);
ret = AVERROR_EXPERIMENTAL;
goto free_and_end;
}
if (avctx->codec_type == AVMEDIA_TYPE_AUDIO &&
(!avctx->time_base.num || !avctx->time_base.den)) {
avctx->time_base.num = 1;
avctx->time_base.den = avctx->sample_rate;
}
if (!HAVE_THREADS)
av_log(avctx, AV_LOG_WARNING, "Warning: not compiled with thread support, using thread emulation\n");
if (CONFIG_FRAME_THREAD_ENCODER && av_codec_is_encoder(avctx->codec)) {
ff_unlock_avcodec(codec); //we will instantiate a few encoders thus kick the counter to prevent false detection of a problem
ret = ff_frame_thread_encoder_init(avctx, options ? *options : NULL);
ff_lock_avcodec(avctx, codec);
if (ret < 0)
goto free_and_end;
}
if (HAVE_THREADS
&& !(avctx->internal->frame_thread_encoder && (avctx->active_thread_type&FF_THREAD_FRAME))) {
ret = ff_thread_init(avctx);
if (ret < 0) {
goto free_and_end;
}
}
if (!HAVE_THREADS && !(codec->capabilities & AV_CODEC_CAP_AUTO_THREADS))
avctx->thread_count = 1;
if (avctx->codec->max_lowres < avctx->lowres || avctx->lowres < 0) {
av_log(avctx, AV_LOG_WARNING, "The maximum value for lowres supported by the decoder is %d\n",
avctx->codec->max_lowres);
avctx->lowres = avctx->codec->max_lowres;
}
#if FF_API_VISMV
if (avctx->debug_mv)
av_log(avctx, AV_LOG_WARNING, "The 'vismv' option is deprecated, "
"see the codecview filter instead.\n");
#endif
// 检查输入参数是否符合【编码器】要求
if (av_codec_is_encoder(avctx->codec)) {
int i;
#if FF_API_CODED_FRAME
FF_DISABLE_DEPRECATION_WARNINGS
avctx->coded_frame = av_frame_alloc();
if (!avctx->coded_frame) {
ret = AVERROR(ENOMEM);
goto free_and_end;
}
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (avctx->time_base.num <= 0 || avctx->time_base.den <= 0) {
av_log(avctx, AV_LOG_ERROR, "The encoder timebase is not set.\n");
ret = AVERROR(EINVAL);
goto free_and_end;
}
// 如果包含采样率参数（表明是音频），检查采样率是否符合要求
if (avctx->codec->sample_fmts) {
// 遍历编码器支持的所有采样率
for (i = 0; avctx->codec->sample_fmts[i] != AV_SAMPLE_FMT_NONE; i++) {
// 如果设置的采样率 == 编码器支持的采样率，跳出循环
if (avctx->sample_fmt == avctx->codec->sample_fmts[i])
break;
if (avctx->channels == 1 &&
av_get_planar_sample_fmt(avctx->sample_fmt) ==
av_get_planar_sample_fmt(avctx->codec->sample_fmts[i])) {
avctx->sample_fmt = avctx->codec->sample_fmts[i];
break;
}
}
// 采样率取值是否正确
if (avctx->codec->sample_fmts[i] == AV_SAMPLE_FMT_NONE) {
char buf[128];
snprintf(buf, sizeof(buf), "%d", avctx->sample_fmt);
av_log(avctx, AV_LOG_ERROR, "Specified sample format %s is invalid or not supported\n",
(char *)av_x_if_null(av_get_sample_fmt_name(avctx->sample_fmt), buf));
ret = AVERROR(EINVAL);
goto free_and_end;
}
}
// 像素格式
if (avctx->codec->pix_fmts) {
for (i = 0; avctx->codec->pix_fmts[i] != AV_PIX_FMT_NONE; i++)
if (avctx->pix_fmt == avctx->codec->pix_fmts[i])
break;
if (avctx->codec->pix_fmts[i] == AV_PIX_FMT_NONE
&& !((avctx->codec_id == AV_CODEC_ID_MJPEG || avctx->codec_id == AV_CODEC_ID_LJPEG)
&& avctx->strict_std_compliance <= FF_COMPLIANCE_UNOFFICIAL)) {
char buf[128];
snprintf(buf, sizeof(buf), "%d", avctx->pix_fmt);
av_log(avctx, AV_LOG_ERROR, "Specified pixel format %s is invalid or not supported\n",
(char *)av_x_if_null(av_get_pix_fmt_name(avctx->pix_fmt), buf));
ret = AVERROR(EINVAL);
goto free_and_end;
}
if (avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ420P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ411P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ422P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ440P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ444P)
avctx->color_range = AVCOL_RANGE_JPEG;
}
// 采样率
if (avctx->codec->supported_samplerates) {
for (i = 0; avctx->codec->supported_samplerates[i] != 0; i++)
if (avctx->sample_rate == avctx->codec->supported_samplerates[i])
break;
if (avctx->codec->supported_samplerates[i] == 0) {
av_log(avctx, AV_LOG_ERROR, "Specified sample rate %d is not supported\n",
avctx->sample_rate);
ret = AVERROR(EINVAL);
goto free_and_end;
}
}
if (avctx->sample_rate < 0) {
av_log(avctx, AV_LOG_ERROR, "Specified sample rate %d is not supported\n",
avctx->sample_rate);
ret = AVERROR(EINVAL);
goto free_and_end;
}
// 声道布局
if (avctx->codec->channel_layouts) {
if (!avctx->channel_layout) {
av_log(avctx, AV_LOG_WARNING, "Channel layout not specified\n");
} else {
for (i = 0; avctx->codec->channel_layouts[i] != 0; i++)
if (avctx->channel_layout == avctx->codec->channel_layouts[i])
break;
if (avctx->codec->channel_layouts[i] == 0) {
char buf[512];
av_get_channel_layout_string(buf, sizeof(buf), -1, avctx->channel_layout);
av_log(avctx, AV_LOG_ERROR, "Specified channel layout '%s' is not supported\n", buf);
ret = AVERROR(EINVAL);
goto free_and_end;
}
}
}
// 声道
if (avctx->channel_layout && avctx->channels) {
int channels = av_get_channel_layout_nb_channels(avctx->channel_layout);
if (channels != avctx->channels) {
char buf[512];
av_get_channel_layout_string(buf, sizeof(buf), -1, avctx->channel_layout);
av_log(avctx, AV_LOG_ERROR,
"Channel layout '%s' with %d channels does not match number of specified channels %d\n",
buf, channels, avctx->channels);
ret = AVERROR(EINVAL);
goto free_and_end;
}
} else if (avctx->channel_layout) {
avctx->channels = av_get_channel_layout_nb_channels(avctx->channel_layout);
}
if (avctx->channels < 0) {
av_log(avctx, AV_LOG_ERROR, "Specified number of channels %d is not supported\n",
avctx->channels);
ret = AVERROR(EINVAL);
goto free_and_end;
}
if(avctx->codec_type == AVMEDIA_TYPE_VIDEO) {
pixdesc = av_pix_fmt_desc_get(avctx->pix_fmt);
if ( avctx->bits_per_raw_sample < 0
|| (avctx->bits_per_raw_sample > 8 && pixdesc->comp[0].depth <= 8)) {
av_log(avctx, AV_LOG_WARNING, "Specified bit depth %d not possible with the specified pixel formats depth %d\n",
avctx->bits_per_raw_sample, pixdesc->comp[0].depth);
avctx->bits_per_raw_sample = pixdesc->comp[0].depth;
}
// 宽高
if (avctx->width <= 0 || avctx->height <= 0) {
av_log(avctx, AV_LOG_ERROR, "dimensions not set\n");
ret = AVERROR(EINVAL);
goto free_and_end;
}
}
// 码率
if ( (avctx->codec_type == AVMEDIA_TYPE_VIDEO || avctx->codec_type == AVMEDIA_TYPE_AUDIO)
&& avctx->bit_rate>0 && avctx->bit_rate<1000) {
av_log(avctx, AV_LOG_WARNING, "Bitrate %"PRId64" is extremely low, maybe you mean %"PRId64"k\n", avctx->bit_rate, avctx->bit_rate);
}
if (!avctx->rc_initial_buffer_occupancy)
avctx->rc_initial_buffer_occupancy = avctx->rc_buffer_size * 3LL / 4;
if (avctx->ticks_per_frame && avctx->time_base.num &&
avctx->ticks_per_frame > INT_MAX / avctx->time_base.num) {
av_log(avctx, AV_LOG_ERROR,
"ticks_per_frame %d too large for the timebase %d/%d.",
avctx->ticks_per_frame,
avctx->time_base.num,
avctx->time_base.den);
goto free_and_end;
}
if (avctx->hw_frames_ctx) {
AVHWFramesContext *frames_ctx = (AVHWFramesContext*)avctx->hw_frames_ctx->data;
if (frames_ctx->format != avctx->pix_fmt) {
av_log(avctx, AV_LOG_ERROR,
"Mismatching AVCodecContext.pix_fmt and AVHWFramesContext.format\n");
ret = AVERROR(EINVAL);
goto free_and_end;
}
if (avctx->sw_pix_fmt != AV_PIX_FMT_NONE &&
avctx->sw_pix_fmt != frames_ctx->sw_format) {
av_log(avctx, AV_LOG_ERROR,
"Mismatching AVCodecContext.sw_pix_fmt (%s) "
"and AVHWFramesContext.sw_format (%s)\n",
av_get_pix_fmt_name(avctx->sw_pix_fmt),
av_get_pix_fmt_name(frames_ctx->sw_format));
ret = AVERROR(EINVAL);
goto free_and_end;
}
avctx->sw_pix_fmt = frames_ctx->sw_format;
}
}
avctx->pts_correction_num_faulty_pts =
avctx->pts_correction_num_faulty_dts = 0;
avctx->pts_correction_last_pts =
avctx->pts_correction_last_dts = INT64_MIN;
if ( !CONFIG_GRAY && avctx->flags & AV_CODEC_FLAG_GRAY
&& avctx->codec_descriptor->type == AVMEDIA_TYPE_VIDEO)
av_log(avctx, AV_LOG_WARNING,
"gray decoding requested but not enabled at configuration time\n");
// 一切检查都无误之后，调用编解码器初始化函数
if ( avctx->codec->init && (!(avctx->active_thread_type&FF_THREAD_FRAME)
|| avctx->internal->frame_thread_encoder)) {
ret = avctx->codec->init(avctx);
if (ret < 0) {
goto free_and_end;
}
}
ret=0;
#if FF_API_AUDIOENC_DELAY
if (av_codec_is_encoder(avctx->codec))
avctx->delay = avctx->initial_padding;
#endif
// 解码器的参数大部分都是由系统自动设定而不是由用户设定，因而不怎么需要检查
if (av_codec_is_decoder(avctx->codec)) {
if (!avctx->bit_rate)
avctx->bit_rate = get_bit_rate(avctx);
/* validate channel layout from the decoder */
if (avctx->channel_layout) {
int channels = av_get_channel_layout_nb_channels(avctx->channel_layout);
if (!avctx->channels)
avctx->channels = channels;
else if (channels != avctx->channels) {
char buf[512];
av_get_channel_layout_string(buf, sizeof(buf), -1, avctx->channel_layout);
av_log(avctx, AV_LOG_WARNING,
"Channel layout '%s' with %d channels does not match specified number of channels %d: "
"ignoring specified channel layout\n",
buf, channels, avctx->channels);
avctx->channel_layout = 0;
}
}
if (avctx->channels && avctx->channels < 0 ||
avctx->channels > FF_SANE_NB_CHANNELS) {
ret = AVERROR(EINVAL);
goto free_and_end;
}
if (avctx->sub_charenc) {
if (avctx->codec_type != AVMEDIA_TYPE_SUBTITLE) {
av_log(avctx, AV_LOG_ERROR, "Character encoding is only "
"supported with subtitles codecs\n");
ret = AVERROR(EINVAL);
goto free_and_end;
} else if (avctx->codec_descriptor->props & AV_CODEC_PROP_BITMAP_SUB) {
av_log(avctx, AV_LOG_WARNING, "Codec '%s' is bitmap-based, "
"subtitles character encoding will be ignored\n",
avctx->codec_descriptor->name);
avctx->sub_charenc_mode = FF_SUB_CHARENC_MODE_DO_NOTHING;
} else {
/* input character encoding is set for a text based subtitle
* codec at this point */
if (avctx->sub_charenc_mode == FF_SUB_CHARENC_MODE_AUTOMATIC)
avctx->sub_charenc_mode = FF_SUB_CHARENC_MODE_PRE_DECODER;
if (avctx->sub_charenc_mode == FF_SUB_CHARENC_MODE_PRE_DECODER) {
#if CONFIG_ICONV
iconv_t cd = iconv_open("UTF-8", avctx->sub_charenc);
if (cd == (iconv_t)-1) {
ret = AVERROR(errno);
av_log(avctx, AV_LOG_ERROR, "Unable to open iconv context "
"with input character encoding \"%s\"\n", avctx->sub_charenc);
goto free_and_end;
}
iconv_close(cd);
#else
av_log(avctx, AV_LOG_ERROR, "Character encoding subtitles "
"conversion needs a libavcodec built with iconv support "
"for this codec\n");
ret = AVERROR(ENOSYS);
goto free_and_end;
#endif
}
}
}
#if FF_API_AVCTX_TIMEBASE
if (avctx->framerate.num > 0 && avctx->framerate.den > 0)
avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
#endif
}
if (codec->priv_data_size > 0 && avctx->priv_data && codec->priv_class) {
av_assert0(*(const AVClass **)avctx->priv_data == codec->priv_class);
}
end:
ff_unlock_avcodec(codec);
if (options) {
av_dict_free(options);
*options = tmp;
}
return ret;
free_and_end:
if (avctx->codec &&
(avctx->codec->caps_internal & FF_CODEC_CAP_INIT_CLEANUP))
avctx->codec->close(avctx);
if (codec->priv_class && codec->priv_data_size)
av_opt_free(avctx->priv_data);
av_opt_free(avctx);
#if FF_API_CODED_FRAME
FF_DISABLE_DEPRECATION_WARNINGS
av_frame_free(&avctx->coded_frame);
FF_ENABLE_DEPRECATION_WARNINGS
#endif
av_dict_free(&tmp);
av_freep(&avctx->priv_data);
if (avctx->internal) {
av_frame_free(&avctx->internal->to_free);
av_frame_free(&avctx->internal->compat_decode_frame);
av_frame_free(&avctx->internal->buffer_frame);
av_packet_free(&avctx->internal->buffer_pkt);
av_packet_free(&avctx->internal->last_pkt_props);
av_packet_free(&avctx->internal->ds.in_pkt);
av_freep(&avctx->internal->pool);
}
av_freep(&avctx->internal);
avctx->codec = NULL;
goto end;
}
其中最主要是调用了 AVCodec 的 init() 初始化，其他还做的有：
av_malloc()
av_codec_is_encoder
当满足了 av_codec_is_encoder()
满足的情况下，进行了参数是否满足编码器规范要求的检查，如：
if (avctx->codec->pix_fmts) {
for (i = 0; avctx->codec->pix_fmts[i] != AV_PIX_FMT_NONE; i++)
if (avctx->pix_fmt == avctx->codec->pix_fmts[i])
break;
if (avctx->codec->pix_fmts[i] == AV_PIX_FMT_NONE
&& !((avctx->codec_id == AV_CODEC_ID_MJPEG || avctx->codec_id == AV_CODEC_ID_LJPEG)
&& avctx->strict_std_compliance <= FF_COMPLIANCE_UNOFFICIAL)) {
char buf[128];
snprintf(buf, sizeof(buf), "%d", avctx->pix_fmt);
av_log(avctx, AV_LOG_ERROR, "Specified pixel format %s is invalid or not supported\n",
(char *)av_x_if_null(av_get_pix_fmt_name(avctx->pix_fmt), buf));
ret = AVERROR(EINVAL);
goto free_and_end;
}
if (avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ420P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ411P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ422P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ440P ||
avctx->codec->pix_fmts[i] == AV_PIX_FMT_YUVJ444P)
avctx->color_range = AVCOL_RANGE_JPEG;
}
将 AVCodecContext 中的 pix_fmt 与编码器 AVCodec 中的 pix_fmts 数组中的元素进行对比，其中 AVCodec 中的 pix_fmts 数组存储了该种编码器支持的像素格式，并且规定以 AV_PIX_FMT_NONE（AV_PIX_FMT_NONE 取值为 - 1）为结尾
static const enum AVPixelFormat pix_fmts_8bit[] = {
AV_PIX_FMT_YUV420P,
AV_PIX_FMT_YUVJ420P,
AV_PIX_FMT_YUV422P,
AV_PIX_FMT_YUVJ422P,
AV_PIX_FMT_YUV444P,
AV_PIX_FMT_YUVJ444P,
AV_PIX_FMT_NV12,
AV_PIX_FMT_NV16,
AV_PIX_FMT_NONE
};
以 libx264 的 pix_fmts 数组为例，从 pix_fmts_8bit 的定义可以看出 libx264 主要支持的是以 YUV 为主的像素格式
avctx->codec->init
AVCodec ff_libx264_encoder = {
.name = "libx264",
.long_name = NULL_IF_CONFIG_SMALL("libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10"),
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_H264,
.priv_data_size = sizeof(X264Context),
.init = X264_init,
.encode2 = X264_frame,
.close = X264_close,
.capabilities = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_AUTO_THREADS,
.priv_class = &x264_class,
.defaults = x264_defaults,
.init_static_data = X264_init_static,
.caps_internal = FF_CODEC_CAP_INIT_THREADSAFE |
FF_CODEC_CAP_INIT_CLEANUP,
};
以 libx264 为例， init
方法对应的是 X264_init
static av_cold int X264_init(AVCodecContext *avctx)
{
X264Context *x4 = avctx->priv_data;
AVCPBProperties *cpb_props;
int sw,sh;
if (avctx->global_quality > 0)
av_log(avctx, AV_LOG_WARNING, "-qscale is ignored, -crf is recommended.\n");
#if CONFIG_LIBX262_ENCODER
if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO) {
x4->params.b_mpeg2 = 1;
x264_param_default_mpeg2(&x4->params);
} else
#endif
x264_param_default(&x4->params);
x4->params.b_deblocking_filter = avctx->flags & AV_CODEC_FLAG_LOOP_FILTER;
if (x4->preset || x4->tune)
if (x264_param_default_preset(&x4->params, x4->preset, x4->tune) < 0) {
int i;
av_log(avctx, AV_LOG_ERROR, "Error setting preset/tune %s/%s.\n", x4->preset, x4->tune);
av_log(avctx, AV_LOG_INFO, "Possible presets:");
for (i = 0; x264_preset_names[i]; i++)
av_log(avctx, AV_LOG_INFO, " %s", x264_preset_names[i]);
av_log(avctx, AV_LOG_INFO, "\n");
av_log(avctx, AV_LOG_INFO, "Possible tunes:");
for (i = 0; x264_tune_names[i]; i++)
av_log(avctx, AV_LOG_INFO, " %s", x264_tune_names[i]);
av_log(avctx, AV_LOG_INFO, "\n");
return AVERROR(EINVAL);
}
if (avctx->level > 0)
x4->params.i_level_idc = avctx->level;
x4->params.pf_log = X264_log;
x4->params.p_log_private = avctx;
x4->params.i_log_level = X264_LOG_DEBUG;
x4->params.i_csp = convert_pix_fmt(avctx->pix_fmt);
PARSE_X264_OPT("weightp", wpredp);
if (avctx->bit_rate) {
x4->params.rc.i_bitrate = avctx->bit_rate / 1000;
x4->params.rc.i_rc_method = X264_RC_ABR;
}
x4->params.rc.i_vbv_buffer_size = avctx->rc_buffer_size / 1000;
x4->params.rc.i_vbv_max_bitrate = avctx->rc_max_rate / 1000;
x4->params.rc.b_stat_write = avctx->flags & AV_CODEC_FLAG_PASS1;
if (avctx->flags & AV_CODEC_FLAG_PASS2) {
x4->params.rc.b_stat_read = 1;
} else {
if (x4->crf >= 0) {
x4->params.rc.i_rc_method = X264_RC_CRF;
x4->params.rc.f_rf_constant = x4->crf;
} else if (x4->cqp >= 0) {
x4->params.rc.i_rc_method = X264_RC_CQP;
x4->params.rc.i_qp_constant = x4->cqp;
}
if (x4->crf_max >= 0)
x4->params.rc.f_rf_constant_max = x4->crf_max;
}
if (avctx->rc_buffer_size && avctx->rc_initial_buffer_occupancy > 0 &&
(avctx->rc_initial_buffer_occupancy <= avctx->rc_buffer_size)) {
x4->params.rc.f_vbv_buffer_init =
(float)avctx->rc_initial_buffer_occupancy / avctx->rc_buffer_size;
}
PARSE_X264_OPT("level", level);
if (avctx->i_quant_factor > 0)
x4->params.rc.f_ip_factor = 1 / fabs(avctx->i_quant_factor);
if (avctx->b_quant_factor > 0)
x4->params.rc.f_pb_factor = avctx->b_quant_factor;
#if FF_API_PRIVATE_OPT
FF_DISABLE_DEPRECATION_WARNINGS
if (avctx->chromaoffset >= 0)
x4->chroma_offset = avctx->chromaoffset;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (x4->chroma_offset >= 0)
x4->params.analyse.i_chroma_qp_offset = x4->chroma_offset;
if (avctx->gop_size >= 0)
x4->params.i_keyint_max = avctx->gop_size;
if (avctx->max_b_frames >= 0)
x4->params.i_bframe = avctx->max_b_frames;
#if FF_API_PRIVATE_OPT
FF_DISABLE_DEPRECATION_WARNINGS
if (avctx->scenechange_threshold >= 0)
x4->scenechange_threshold = avctx->scenechange_threshold;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (x4->scenechange_threshold >= 0)
x4->params.i_scenecut_threshold = x4->scenechange_threshold;
if (avctx->qmin >= 0)
x4->params.rc.i_qp_min = avctx->qmin;
if (avctx->qmax >= 0)
x4->params.rc.i_qp_max = avctx->qmax;
if (avctx->max_qdiff >= 0)
x4->params.rc.i_qp_step = avctx->max_qdiff;
if (avctx->qblur >= 0)
x4->params.rc.f_qblur = avctx->qblur; /* temporally blur quants */
if (avctx->qcompress >= 0)
x4->params.rc.f_qcompress = avctx->qcompress; /* 0.0 => cbr, 1.0 => constant qp */
if (avctx->refs >= 0)
x4->params.i_frame_reference = avctx->refs;
else if (x4->level) {
int i;
int mbn = AV_CEIL_RSHIFT(avctx->width, 4) * AV_CEIL_RSHIFT(avctx->height, 4);
int level_id = -1;
char *tail;
int scale = X264_BUILD < 129 ? 384 : 1;
if (!strcmp(x4->level, "1b")) {
level_id = 9;
} else if (strlen(x4->level) <= 3){
level_id = av_strtod(x4->level, &tail) * 10 + 0.5;
if (*tail)
level_id = -1;
}
if (level_id <= 0)
av_log(avctx, AV_LOG_WARNING, "Failed to parse level\n");
for (i = 0; i<x264_levels[i].level_idc; i++)
if (x264_levels[i].level_idc == level_id)
x4->params.i_frame_reference = av_clip(x264_levels[i].dpb / mbn / scale, 1, x4->params.i_frame_reference);
}
if (avctx->trellis >= 0)
x4->params.analyse.i_trellis = avctx->trellis;
if (avctx->me_range >= 0)
x4->params.analyse.i_me_range = avctx->me_range;
#if FF_API_PRIVATE_OPT
FF_DISABLE_DEPRECATION_WARNINGS
if (avctx->noise_reduction >= 0)
x4->noise_reduction = avctx->noise_reduction;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (x4->noise_reduction >= 0)
x4->params.analyse.i_noise_reduction = x4->noise_reduction;
if (avctx->me_subpel_quality >= 0)
x4->params.analyse.i_subpel_refine = avctx->me_subpel_quality;
#if FF_API_PRIVATE_OPT
FF_DISABLE_DEPRECATION_WARNINGS
if (avctx->b_frame_strategy >= 0)
x4->b_frame_strategy = avctx->b_frame_strategy;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (avctx->keyint_min >= 0)
x4->params.i_keyint_min = avctx->keyint_min;
#if FF_API_CODER_TYPE
FF_DISABLE_DEPRECATION_WARNINGS
if (avctx->coder_type >= 0)
x4->coder = avctx->coder_type == FF_CODER_TYPE_AC;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
if (avctx->me_cmp >= 0)
x4->params.analyse.b_chroma_me = avctx->me_cmp & FF_CMP_CHROMA;
if (x4->aq_mode >= 0)
x4->params.rc.i_aq_mode = x4->aq_mode;
if (x4->aq_strength >= 0)
x4->params.rc.f_aq_strength = x4->aq_strength;
PARSE_X264_OPT("psy-rd", psy_rd);
PARSE_X264_OPT("deblock", deblock);
PARSE_X264_OPT("partitions", partitions);
PARSE_X264_OPT("stats", stats);
if (x4->psy >= 0)
x4->params.analyse.b_psy = x4->psy;
if (x4->rc_lookahead >= 0)
x4->params.rc.i_lookahead = x4->rc_lookahead;
if (x4->weightp >= 0)
x4->params.analyse.i_weighted_pred = x4->weightp;
if (x4->weightb >= 0)
x4->params.analyse.b_weighted_bipred = x4->weightb;
if (x4->cplxblur >= 0)
x4->params.rc.f_complexity_blur = x4->cplxblur;
if (x4->ssim >= 0)
x4->params.analyse.b_ssim = x4->ssim;
if (x4->intra_refresh >= 0)
x4->params.b_intra_refresh = x4->intra_refresh;
if (x4->bluray_compat >= 0) {
x4->params.b_bluray_compat = x4->bluray_compat;
x4->params.b_vfr_input = 0;
}
if (x4->avcintra_class >= 0)
#if X264_BUILD >= 142
x4->params.i_avcintra_class = x4->avcintra_class;
#else
av_log(avctx, AV_LOG_ERROR,
"x264 too old for AVC Intra, at least version 142 needed\n");
#endif
if (x4->b_bias != INT_MIN)
x4->params.i_bframe_bias = x4->b_bias;
if (x4->b_pyramid >= 0)
x4->params.i_bframe_pyramid = x4->b_pyramid;
if (x4->mixed_refs >= 0)
x4->params.analyse.b_mixed_references = x4->mixed_refs;
if (x4->dct8x8 >= 0)
x4->params.analyse.b_transform_8x8 = x4->dct8x8;
if (x4->fast_pskip >= 0)
x4->params.analyse.b_fast_pskip = x4->fast_pskip;
if (x4->aud >= 0)
x4->params.b_aud = x4->aud;
if (x4->mbtree >= 0)
x4->params.rc.b_mb_tree = x4->mbtree;
if (x4->direct_pred >= 0)
x4->params.analyse.i_direct_mv_pred = x4->direct_pred;
if (x4->slice_max_size >= 0)
x4->params.i_slice_max_size = x4->slice_max_size;
if (x4->fastfirstpass)
x264_param_apply_fastfirstpass(&x4->params);
/* Allow specifying the x264 profile through AVCodecContext. */
if (!x4->profile)
switch (avctx->profile) {
case FF_PROFILE_H264_BASELINE:
x4->profile = av_strdup("baseline");
break;
case FF_PROFILE_H264_HIGH:
x4->profile = av_strdup("high");
break;
case FF_PROFILE_H264_HIGH_10:
x4->profile = av_strdup("high10");
break;
case FF_PROFILE_H264_HIGH_422:
x4->profile = av_strdup("high422");
break;
case FF_PROFILE_H264_HIGH_444:
x4->profile = av_strdup("high444");
break;
case FF_PROFILE_H264_MAIN:
x4->profile = av_strdup("main");
break;
default:
break;
}
if (x4->nal_hrd >= 0)
x4->params.i_nal_hrd = x4->nal_hrd;
if (x4->motion_est >= 0) {
x4->params.analyse.i_me_method = x4->motion_est;
#if FF_API_MOTION_EST
FF_DISABLE_DEPRECATION_WARNINGS
} else {
if (avctx->me_method == ME_EPZS)
x4->params.analyse.i_me_method = X264_ME_DIA;
else if (avctx->me_method == ME_HEX)
x4->params.analyse.i_me_method = X264_ME_HEX;
else if (avctx->me_method == ME_UMH)
x4->params.analyse.i_me_method = X264_ME_UMH;
else if (avctx->me_method == ME_FULL)
x4->params.analyse.i_me_method = X264_ME_ESA;
else if (avctx->me_method == ME_TESA)
x4->params.analyse.i_me_method = X264_ME_TESA;
FF_ENABLE_DEPRECATION_WARNINGS
#endif
}
if (x4->coder >= 0)
x4->params.b_cabac = x4->coder;
if (x4->b_frame_strategy >= 0)
x4->params.i_bframe_adaptive = x4->b_frame_strategy;
if (x4->profile)
if (x264_param_apply_profile(&x4->params, x4->profile) < 0) {
int i;
av_log(avctx, AV_LOG_ERROR, "Error setting profile %s.\n", x4->profile);
av_log(avctx, AV_LOG_INFO, "Possible profiles:");
for (i = 0; x264_profile_names[i]; i++)
av_log(avctx, AV_LOG_INFO, " %s", x264_profile_names[i]);
av_log(avctx, AV_LOG_INFO, "\n");
return AVERROR(EINVAL);
}
x4->params.i_width = avctx->width;
x4->params.i_height = avctx->height;
av_reduce(&sw, &sh, avctx->sample_aspect_ratio.num, avctx->sample_aspect_ratio.den, 4096);
x4->params.vui.i_sar_width = sw;
x4->params.vui.i_sar_height = sh;
x4->params.i_timebase_den = avctx->time_base.den;
x4->params.i_timebase_num = avctx->time_base.num;
x4->params.i_fps_num = avctx->time_base.den;
x4->params.i_fps_den = avctx->time_base.num * avctx->ticks_per_frame;
x4->params.analyse.b_psnr = avctx->flags & AV_CODEC_FLAG_PSNR;
x4->params.i_threads = avctx->thread_count;
if (avctx->thread_type)
x4->params.b_sliced_threads = avctx->thread_type == FF_THREAD_SLICE;
x4->params.b_interlaced = avctx->flags & AV_CODEC_FLAG_INTERLACED_DCT;
x4->params.b_open_gop = !(avctx->flags & AV_CODEC_FLAG_CLOSED_GOP);
x4->params.i_slice_count = avctx->slices;
x4->params.vui.b_fullrange = avctx->pix_fmt == AV_PIX_FMT_YUVJ420P ||
avctx->pix_fmt == AV_PIX_FMT_YUVJ422P ||
avctx->pix_fmt == AV_PIX_FMT_YUVJ444P ||
avctx->color_range == AVCOL_RANGE_JPEG;
if (avctx->colorspace != AVCOL_SPC_UNSPECIFIED)
x4->params.vui.i_colmatrix = avctx->colorspace;
if (avctx->color_primaries != AVCOL_PRI_UNSPECIFIED)
x4->params.vui.i_colorprim = avctx->color_primaries;
if (avctx->color_trc != AVCOL_TRC_UNSPECIFIED)
x4->params.vui.i_transfer = avctx->color_trc;
if (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER)
x4->params.b_repeat_headers = 0;
if(x4->x264opts){
const char *p= x4->x264opts;
while(p){
char param[4096]={0}, val[4096]={0};
if(sscanf(p, "%4095[^:=]=%4095[^:]", param, val) == 1){
OPT_STR(param, "1");
}else
OPT_STR(param, val);
p= strchr(p, ':');
p+=!!p;
}
}
if (x4->x264_params) {
AVDictionary *dict = NULL;
AVDictionaryEntry *en = NULL;
if (!av_dict_parse_string(&dict, x4->x264_params, "=", ":", 0)) {
while ((en = av_dict_get(dict, "", en, AV_DICT_IGNORE_SUFFIX))) {
if (x264_param_parse(&x4->params, en->key, en->value) < 0)
av_log(avctx, AV_LOG_WARNING,
"Error parsing option '%s = %s'.\n",
en->key, en->value);
}
av_dict_free(&dict);
}
}
// update AVCodecContext with x264 parameters
avctx->has_b_frames = x4->params.i_bframe ?
x4->params.i_bframe_pyramid ? 2 : 1 : 0;
if (avctx->max_b_frames < 0)
avctx->max_b_frames = 0;
avctx->bit_rate = x4->params.rc.i_bitrate*1000;
x4->enc = x264_encoder_open(&x4->params);
if (!x4->enc)
return AVERROR_EXTERNAL;
if (avctx->flags & AV_CODEC_FLAG_GLOBAL_HEADER) {
x264_nal_t *nal;
uint8_t *p;
int nnal, s, i;
s = x264_encoder_headers(x4->enc, &nal, &nnal);
avctx->extradata = p = av_mallocz(s + AV_INPUT_BUFFER_PADDING_SIZE);
if (!p)
return AVERROR(ENOMEM);
for (i = 0; i < nnal; i++) {
/* Don't put the SEI in extradata. */
if (nal[i].i_type == NAL_SEI) {
av_log(avctx, AV_LOG_INFO, "%s\n", nal[i].p_payload+25);
x4->sei_size = nal[i].i_payload;
x4->sei = av_malloc(x4->sei_size);
if (!x4->sei)
return AVERROR(ENOMEM);
memcpy(x4->sei, nal[i].p_payload, nal[i].i_payload);
continue;
}
memcpy(p, nal[i].p_payload, nal[i].i_payload);
p += nal[i].i_payload;
}
avctx->extradata_size = p - avctx->extradata;
}
cpb_props = ff_add_cpb_side_data(avctx);
if (!cpb_props)
return AVERROR(ENOMEM);
cpb_props->buffer_size = x4->params.rc.i_vbv_buffer_size * 1000;
cpb_props->max_bitrate = x4->params.rc.i_vbv_max_bitrate * 1000;
cpb_props->avg_bitrate = x4->params.rc.i_bitrate * 1000;
return 0;
}
大概的工作
- 设置 X264Context 的参数。X264Context 主要完成了 libx264 和 FFmpeg 对接的功能。可以看出代码主要在设置一个 params 结构体变量，该变量的类型即是 x264 中存储参数的结构体 x264_param_t。
- 调用 libx264 的 API 进行编码器的初始化工作。例如调用 x264_param_default() 设置默认参数，调用 x264_param_apply_profile() 设置 profile，调用 x264_encoder_open() 打开编码器等等。
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