Quoting Peter Große (2017-01-27 20:16:31)
> On Fri, 27 Jan 2017 19:34:42 +0100
> Anton Khirnov <[email protected]> wrote:
>
> > If we did, I don't remember the conclusion :)
> >
> > Anyway, I agree that this is a misuse of metadata. There are at least
> > two methods for passing the stream bitrate to the muxer -- the
> > AVCodecParameters.bit_rate field and the AV_PKT_DATA_CPB_PROPERTIES side
> > data.
> >
> > IIUC, the problem you're trying to solve is that avconv does not set the
> > bit_rate field in certain situations. If that's the case, that should be
> > fixed in avconv. We should not design our muxer behaviour around
> > limitations of one specific caller.
> >
> > If you describe more fully what's the situation where bit_rate is not
> > set properly, I might have some more specific ideas for handling this.
>
> Hm I see.
>
> I tried to remux an already encoded MKV stream pulled from an icecast server.
> So I used -codec copy and the upstream container didn't contain bitrate
> metadata.
> Avprobe output from a stream dump see below [1].
>
> For DASH I needed to hint the average bandwith of a stream in the manifest.
> Calculating this from the first segment created might be an option, but I felt
> more comfortable explicitly hinting the bandwidth via a metadata option.
>
> Other than for the manifest, this value isn't used anywhere, as far as I
> remember.
>
> I thought the parser for the adaptation_set option is complex enough. I tried
> to avoid writing another one for adding metadata to individual streams.
>
> Yes, the obvious solution would be to fix the upstream encoder. But I'm not
> sure, whether I get all possible codecs to write an average bitrate to their
> stream metadata.
Actually I'd say the issue is just that matroska does not have a field
for storing the bitrate. And the right workaround for that issue would
be allowing avconv to override the muxer bitrate for streamcopy.
The following code should make -b work for streamcopy, then you can just
pull the information from AVCodecParameters.bit_rate:
diff --git a/avconv.c b/avconv.c
index fe60625..94b6da2 100644
--- a/avconv.c
+++ b/avconv.c
@@ -1852,6 +1852,9 @@ static int init_output_stream_streamcopy(OutputStream
*ost)
ost->st->time_base = ist->st->time_base;
+ if (ost->bitrate_override)
+ par_dst->bit_rate = ost->bitrate_override;
+
if (ist->st->nb_side_data) {
ost->st->side_data = av_realloc_array(NULL, ist->st->nb_side_data,
sizeof(*ist->st->side_data));
diff --git a/avconv.h b/avconv.h
index 6360f76..3c3f0ef 100644
--- a/avconv.h
+++ b/avconv.h
@@ -162,6 +162,8 @@ typedef struct OptionsContext {
int nb_sample_fmts;
SpecifierOpt *qscale;
int nb_qscale;
+ SpecifierOpt *bitrates;
+ int nb_bitrates;
SpecifierOpt *forced_key_frames;
int nb_forced_key_frames;
SpecifierOpt *force_fps;
@@ -382,6 +384,9 @@ typedef struct OutputStream {
int forced_kf_index;
char *forced_keyframes;
+ // the bitrate to send to the muxer for streamcopy
+ int bitrate_override;
+
char *logfile_prefix;
FILE *logfile;
diff --git a/avconv_opt.c b/avconv_opt.c
index 8b43f0f..e078a0b 100644
--- a/avconv_opt.c
+++ b/avconv_opt.c
@@ -952,6 +952,7 @@ static OutputStream *new_output_stream(OptionsContext *o,
AVFormatContext *oc, e
const char *bsfs = NULL;
char *next, *codec_tag = NULL;
double qscale = -1;
+ int bitrate = 0;
if (!st) {
av_log(NULL, AV_LOG_FATAL, "Could not alloc stream.\n");
@@ -1091,6 +1092,14 @@ static OutputStream *new_output_stream(OptionsContext
*o, AVFormatContext *oc, e
ost->enc_ctx->global_quality = FF_QP2LAMBDA * qscale;
}
+ MATCH_PER_STREAM_OPT(bitrates, i, bitrate, oc, st);
+ if (bitrate > 0) {
+ if (ost->stream_copy)
+ ost->bitrate_override = bitrate;
+ else
+ ost->enc_ctx->bit_rate = bitrate;
+ }
+
ost->max_muxing_queue_size = 128;
MATCH_PER_STREAM_OPT(max_muxing_queue_size, i, ost->max_muxing_queue_size,
oc, st);
ost->max_muxing_queue_size *= sizeof(AVPacket);
@@ -2570,6 +2579,8 @@ const OptionDef options[] = {
{ "qscale", HAS_ARG | OPT_EXPERT | OPT_DOUBLE |
OPT_SPEC | OPT_OUTPUT, { .off =
OFFSET(qscale) },
"use fixed quality scale (VBR)", "q" },
+ { "b", HAS_ARG | OPT_INT | OPT_SPEC | OPT_OUTPUT, { .off =
OFFSET(bitrates) },
+ "set stream bitrate in bits/second", "bitrate" },
{ "filter", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off =
OFFSET(filters) },
"set stream filterchain", "filter_list" },
{ "filter_script", HAS_ARG | OPT_STRING | OPT_SPEC | OPT_OUTPUT, { .off =
OFFSET(filter_scripts) },
--
Anton Khirnov
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