[FFmpeg-user] Transcode with the some properties
Boris
ndjoreboris at gmail.com
Mon Nov 4 11:29:10 EET 2019
Hello,
I want to transcode video with exactly the same properties of the input
video in the output video.
I use the transcoding.cc code. In the static int open_output_file(const
char *filename) function, I set encoder parameters like this :
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
{
enc_ctx->height = dec_ctx->height;
enc_ctx->width = dec_ctx->width;
enc_ctx->sample_aspect_ratio =
dec_ctx->sample_aspect_ratio;
enc_ctx->global_quality=dec_ctx->global_quality;
enc_ctx->gop_size=dec_ctx->gop_size;
enc_ctx->bit_rate=dec_ctx->bit_rate;
enc_ctx->time_base=dec_ctx->time_base;
enc_ctx->delay=dec_ctx->delay;
//**********************************************
enc_ctx->rc_max_rate=dec_ctx->rc_max_rate;
enc_ctx->rc_min_rate=dec_ctx->rc_min_rate;
/* take first format from list of supported
formats */
if (encoder->pix_fmts)
{
enc_ctx->pix_fmt =
encoder->pix_fmts[0];
}
else
{
enc_ctx->pix_fmt = dec_ctx->pix_fmt;
}
// video time_base can be set to whatever
is handy and supported by encoder
// enc_ctx->time_base =
av_inv_q(dec_ctx->framerate);
}
else
{
enc_ctx->sample_rate = dec_ctx->sample_rate;
enc_ctx->channel_layout =
dec_ctx->channel_layout;
enc_ctx->channels =
av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
/* take first format from list of supported
formats */
enc_ctx->sample_fmt =
encoder->sample_fmts[0];
enc_ctx->time_base = (AVRational){1,
enc_ctx->sample_rate};
}
/* Third parameter can be used to pass settings to
encoder */
ret = avcodec_open2(enc_ctx, encoder, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Cannot open
video encoder for stream #%u\n", i);
return ret;
}
ret =
avcodec_parameters_from_context(out_stream->codecpar, enc_ctx);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Failed to copy
encoder parameters to output stream #%u\n", i);
return ret;
}
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
enc_ctx->flags |=
AV_CODEC_FLAG_GLOBAL_HEADER;
out_stream->time_base = enc_ctx->time_base;
But when I run exiftool on output video and on input video, some values
like video duration, encoder, bit rate, are differente.
Can someone tells me how can I do to keep the same parameters (metada) of
the input video in the output video, please?
The entire open_output_file function is the following :
static int open_output_file(const char *filename)
{
AVStream *out_stream;
AVStream *in_stream;
AVCodecContext *dec_ctx, *enc_ctx;
AVCodec *encoder;
int ret;
unsigned int i;
ofmt_ctx = NULL;
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, filename);
if (!ofmt_ctx)
{
av_log(NULL, AV_LOG_ERROR, "Could not create output
context\n");
return AVERROR_UNKNOWN;
}
for (i = 0; i < ifmt_ctx->nb_streams; i++)
{
out_stream = avformat_new_stream(ofmt_ctx, NULL);
if (!out_stream)
{
av_log(NULL, AV_LOG_ERROR, "Failed allocating
output stream\n");
return AVERROR_UNKNOWN;
}
in_stream = ifmt_ctx->streams[i];
dec_ctx = stream_ctx[i].dec_ctx;
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO ||
dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO)
{
//AVCodecID codec_id = dec_ctx->codec_type ==
AVMEDIA_TYPE_VIDEO ? AV_CODEC_ID_MPEG4:dec_ctx->codec_id;
/* in this example, we choose transcoding to same
codec */
//encoder = dec_ctx->codec_type ==
AVMEDIA_TYPE_VIDEO ?
avcodec_find_encoder(AV_CODEC_ID_H264):avcodec_find_encoder(dec_ctx->codec_id);//(AV_CODEC_ID_MPEG4):avcodec_find_encoder(dec_ctx->codec_id);
encoder = dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
?
avcodec_find_encoder(AV_CODEC_ID_MPEG4):avcodec_find_encoder(dec_ctx->codec_id);
// if(dec_ctx->codec_type ==
AVMEDIA_TYPE_VIDEO){encoder=avcodec_find_encoder(AV_CODEC_ID_MPEG4);}else{encoder=avcodec_find_encoder(dec_ctx->codec_id);}
//encoder = avcodec_find_encoder(dec_ctx->codec_id);
if (!encoder)
{
av_log(NULL, AV_LOG_FATAL, "Necessary
encoder not found\n");
return AVERROR_INVALIDDATA;
}
enc_ctx = avcodec_alloc_context3(encoder);
if (!enc_ctx)
{
av_log(NULL, AV_LOG_FATAL, "Failed to
allocate the encoder context\n");
return AVERROR(ENOMEM);
}
/* In this example, we transcode to same properties
(picture size,
* sample rate etc.). These properties can be
changed for output
* streams easily using filters */
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO)
{
enc_ctx->height = dec_ctx->height;
enc_ctx->width = dec_ctx->width;
enc_ctx->sample_aspect_ratio =
dec_ctx->sample_aspect_ratio;
enc_ctx->global_quality=dec_ctx->global_quality;
enc_ctx->gop_size=dec_ctx->gop_size;
enc_ctx->bit_rate=dec_ctx->bit_rate;
enc_ctx->time_base=dec_ctx->time_base;
enc_ctx->delay=dec_ctx->delay;
//**********************************************
enc_ctx->rc_max_rate=dec_ctx->rc_max_rate;
enc_ctx->rc_min_rate=dec_ctx->rc_min_rate;
/* take first format from list of supported
formats */
if (encoder->pix_fmts)
{
enc_ctx->pix_fmt =
encoder->pix_fmts[0];
}
else
{
enc_ctx->pix_fmt = dec_ctx->pix_fmt;
}
// video time_base can be set to whatever
is handy and supported by encoder
// enc_ctx->time_base =
av_inv_q(dec_ctx->framerate);
}
else
{
enc_ctx->sample_rate = dec_ctx->sample_rate;
enc_ctx->channel_layout =
dec_ctx->channel_layout;
enc_ctx->channels =
av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
/* take first format from list of supported
formats */
enc_ctx->sample_fmt =
encoder->sample_fmts[0];
enc_ctx->time_base = (AVRational){1,
enc_ctx->sample_rate};
}
/* Third parameter can be used to pass settings to
encoder */
ret = avcodec_open2(enc_ctx, encoder, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Cannot open
video encoder for stream #%u\n", i);
return ret;
}
ret =
avcodec_parameters_from_context(out_stream->codecpar, enc_ctx);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Failed to copy
encoder parameters to output stream #%u\n", i);
return ret;
}
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
enc_ctx->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
out_stream->time_base = enc_ctx->time_base;
stream_ctx[i].enc_ctx = enc_ctx;
}
else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN)
{
av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d
is of unknown type, cannot proceed\n", i);
return AVERROR_INVALIDDATA;
}
else
{
// if this stream must be remuxed
ret = avcodec_parameters_copy(out_stream->codecpar,
in_stream->codecpar);
//ifmt_ctx->streams[i]->codec);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Copying
parameters for stream #%u failed\n", i);
return ret;
}
out_stream->time_base = in_stream->time_base;
}
}
av_dump_format(ofmt_ctx, 0, filename, 1);
if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
{
ret = avio_open(&ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Could not open output
file '%s'", filename);
return ret;
}
}
/* init muxer, write output file header */
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0)
{
av_log(NULL, AV_LOG_ERROR, "Error occurred when opening
output file\n");
return ret;
}
return 0;
}
Rgards
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