Hi to all I'm trying to encode some image into a mpg1 video file.
When I start the program I get lots of "buffer underflow" errors so:
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=120 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=452 size=1849
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=215 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=206 size=1849
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=5 size=36
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=342 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=136 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=91 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=1734 size=1849
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=258 size=377
[mpeg @ 0x9287f0]buffer underflow i=0 bufi=1488 size=1849
In the code I set these parameters:
void MovieRecorderBase::ffmpegOpenMovie( FrameRate frameRate )
{
AVOutputFormat * format = 0;
int bitrate = 0;
int gopSize = 10;
PixelFormat pixelFormat = PIX_FMT_YUV420P;
int bFrames = 0;
int extraFlags = 0;
m_outputBufferSize = m_width * m_height;
switch ( m_format ) {
case HuffYUV: /* no intra frames */
format = guess_format( "avi", NULL, NULL );
m_fmt = guess_format( "avi", NULL, NULL );
if ( format )
format->video_codec = CODEC_ID_FFVHUFF;
pixelFormat = PIX_FMT_YUV422P;
m_outputBufferSize *= 3;
break;
case MPEG1:
if ( frameRate < FR_NTSC_FILM ) {
std::string str = boost::str(
boost::format("MovieRecorderBase::ffmpegOpenMovie(): FrameRate too low for
MPEG1 (%d, use %d)" ) % frameRate % FR_NTSC_FILM );
LOG_ERR((char *)str.c_str());
return;
}
format = guess_format( "mpeg", NULL, NULL );
m_fmt = guess_format( "mpeg", NULL, NULL );
if ( format )
format->video_codec = CODEC_ID_MPEG1VIDEO;
bFrames = 1;
gopSize = 12;
bitrate = (int)(8 * 0.57 * m_width * m_height
* 25. * ((double)s_frameRateNumerator[frameRate]
/
(double)s_frameRateDenominator[frameRate]) );
break;
case MPEG4:
format = guess_format( "mp4", NULL, NULL );
m_fmt = guess_format( "mp4", NULL, NULL );
if ( format )
format->video_codec = CODEC_ID_MPEG4;
bFrames = 2;
// FIXME: first fix the first blank frame bug, then uncomment
// gopSize = 30;
bitrate = (int)(8 * 0.35 * m_width * m_height
* 25. * ((double)s_frameRateNumerator[frameRate]
/
(double)s_frameRateDenominator[frameRate]) );
extraFlags = CODEC_FLAG_GLOBAL_HEADER
| CODEC_FLAG_4MV
| CODEC_FLAG_TRELLIS_QUANT
| CODEC_FLAG_AC_PRED;
break;
default:
std::string str = boost::str( boost::format(
"MovieRecorderBase::ffmpegOpenMovie(): Unsupported movie format %d." ) %
m_format );
LOG_ERR((char *)str.c_str());
return;
}
if ( !format ) {
std::string str = boost::str( boost::format(
"MovieRecorderBase::ffmpegOpenMovie(): Movie format %d not recognized by
ffmpeg." ) % m_format );
LOG_ERR((char *)str.c_str());
return;
}
//check for a video codec available
if ( format->video_codec == CODEC_ID_NONE ) {
std::string str = boost::str( boost::format(
"MovieRecorderBase::ffmpegOpenMovie(): Movie format %d not associated with
any video codec!" ) % m_format );
LOG_ERR((char *)str.c_str());
return;
}
// check for an audio codec available
if ( format->audio_codec == CODEC_ID_NONE ) {
std::string str = boost::str( boost::format(
"MovieRecorderBase::ffmpegOpenMovie(): Movie format %d not associated with
any audio codec!" ) % m_format );
LOG_ERR((char *)str.c_str());
return;
}
assert( !m_outputBuffer );
m_outputBuffer = (unsigned char *)av_malloc( m_outputBufferSize );
if ( !m_outputBuffer ) {
LOG_ERR("MovieRecorderBase::constructor: Error allocating output
buffer.");
return;
}
// allocate output media context
assert( !m_context );
m_context = av_alloc_format_context();
if ( !m_context ) {
LOG_ERR("MovieRecorderBase::ffmpegOpenMovie(): Cannot allocate
format context.");
return;
}
m_context->oformat = format;
std::string filename = m_movieNameBase + m_movieNameExtension;
snprintf( m_context->filename, sizeof(m_context->filename), "%s",
filename.c_str() );
// add video stream
assert( !m_stream );
m_stream = av_new_stream( m_context, 0 );
if ( !m_stream ) {
LOG_ERR("MovieRecorderBase::ffmpegOpenMovie(): Cannot add video
stream.");
return;
}
AVCodecContext *codecCtx = m_stream->codec;
codecCtx->codec_id = format->video_codec;
codecCtx->codec_type = CODEC_TYPE_VIDEO;
codecCtx->bit_rate = bitrate;
codecCtx->bit_rate_tolerance = codecCtx->bit_rate / 5;// to see
codecCtx->width = m_width;
codecCtx->height = m_height;
codecCtx->time_base.den =
s_frameRateNumerator[frameRate];//(AVRational){1/x}
codecCtx->time_base.num = s_frameRateDenominator[frameRate];
codecCtx->gop_size = gopSize;
codecCtx->pix_fmt = pixelFormat;
codecCtx->max_b_frames = bFrames;
codecCtx->b_frame_strategy = 1;
codecCtx->mb_decision = 2;
codecCtx->strict_std_compliance = FF_COMPLIANCE_NORMAL;
codecCtx->flags |= extraFlags;
In the switch I choose MPEG1 case.
For the bit rate I implement this formula
bpp = bitrate / ( image_width * image_height * 8 * frames_per_second )
bpp = "bits per pixel". I set bpp to 0.57 and determine the bitrate.
What is wrong?
Regards
--
Franco
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