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声明
/**
* Open an input stream and read the header. The codecs are not opened.
* The stream must be closed with avformat_close_input().
*
* @param ps Pointer to user-supplied AVFormatContext (allocated by avformat_alloc_context).
* May be a pointer to NULL, in which case an AVFormatContext is allocated by this
* function and written into ps.
* Note that a user-supplied AVFormatContext will be freed on failure.
* @param url URL of the stream to open.
* @param fmt If non-NULL, this parameter forces a specific input format.
* Otherwise the format is autodetected.
* @param options A dictionary filled with AVFormatContext and demuxer-private options.
* On return this parameter will be destroyed and replaced with a dict containing
* options that were not found. May be NULL.
*
* @return 0 on success, a negative AVERROR on failure.
*
* @note If you want to use custom IO, preallocate the format context and set its pb field.
*/
int avformat_open_input(AVFormatContext **ps, const char *url, AVInputFormat *fmt, AVDictionary **options);
定义
int avformat_open_input(AVFormatContext **ps, const char *filename,
AVInputFormat *fmt, AVDictionary **options)
{
AVFormatContext *s = *ps;
int i, ret = 0;
AVDictionary *tmp = NULL;
ID3v2ExtraMeta *id3v2_extra_meta = NULL;
if (!s && !(s = avformat_alloc_context()))
return AVERROR(ENOMEM);
if (!s->av_class) {
av_log(NULL, AV_LOG_ERROR, “Input context has not been properly allocated by avformat_alloc_context() and is not NULL either\n”);
return AVERROR(EINVAL);
}
if (fmt)
s->iformat = fmt;
if (options)
av_dict_copy(&tmp, *options, 0);
if (s->pb) // must be before any goto fail
s->flags |= AVFMT_FLAG_CUSTOM_IO;
if ((ret = av_opt_set_dict(s, &tmp)) < 0)
goto fail;
av_strlcpy(s->filename, filename ? filename : “”, sizeof(s->filename));
if ((ret = init_input(s, filename, &tmp)) < 0)
goto fail;
s->probe_score = ret;
if (!s->protocol_whitelist && s->pb && s->pb->protocol_whitelist) {
s->protocol_whitelist = av_strdup(s->pb->protocol_whitelist);
if (!s->protocol_whitelist) {
ret = AVERROR(ENOMEM);
goto fail;
}
}
if (!s->protocol_blacklist && s->pb && s->pb->protocol_blacklist) {
s->protocol_blacklist = av_strdup(s->pb->protocol_blacklist);
if (!s->protocol_blacklist) {
ret = AVERROR(ENOMEM);
goto fail;
}
}
if (s->format_whitelist && av_match_list(s->iformat->name, s->format_whitelist, ‘,’) <= 0) {
av_log(s, AV_LOG_ERROR, “Format not on whitelist \’%s\’\n”, s->format_whitelist);
ret = AVERROR(EINVAL);
goto fail;
}
avio_skip(s->pb, s->skip_initial_bytes);
/* Check filename in case an image number is expected. */
if (s->iformat->flags & AVFMT_NEEDNUMBER) {
if (!av_filename_number_test(filename)) {
ret = AVERROR(EINVAL);
goto fail;
}
}
s->duration = s->start_time = AV_NOPTS_VALUE;
/* Allocate private data. */
if (s->iformat->priv_data_size > 0) {
if (!(s->priv_data = av_mallocz(s->iformat->priv_data_size))) {
ret = AVERROR(ENOMEM);
goto fail;
}
if (s->iformat->priv_class) {
*(const AVClass **) s->priv_data = s->iformat->priv_class;
av_opt_set_defaults(s->priv_data);
if ((ret = av_opt_set_dict(s->priv_data, &tmp)) < 0)
goto fail;
}
}
/* e.g. AVFMT_NOFILE formats will not have a AVIOContext */
if (s->pb)
ff_id3v2_read_dict(s->pb, &s->internal->id3v2_meta, ID3v2_DEFAULT_MAGIC, &id3v2_extra_meta);
if (!(s->flags&AVFMT_FLAG_PRIV_OPT) && s->iformat->read_header)
if ((ret = s->iformat->read_header(s)) < 0)
goto fail;
if (!s->metadata) {
s->metadata = s->internal->id3v2_meta;
s->internal->id3v2_meta = NULL;
} else if (s->internal->id3v2_meta) {
int level = AV_LOG_WARNING;
if (s->error_recognition & AV_EF_COMPLIANT)
level = AV_LOG_ERROR;
av_log(s, level, “Discarding ID3 tags because more suitable tags were found.\n”);
av_dict_free(&s->internal->id3v2_meta);
if (s->error_recognition & AV_EF_EXPLODE)
return AVERROR_INVALIDDATA;
}
if (id3v2_extra_meta) {
if (!strcmp(s->iformat->name, “mp3”) || !strcmp(s->iformat->name, “aac”) ||
!strcmp(s->iformat->name, “tta”)) {
if ((ret = ff_id3v2_parse_apic(s, &id3v2_extra_meta)) < 0)
goto fail;
if ((ret = ff_id3v2_parse_chapters(s, &id3v2_extra_meta)) < 0)
goto fail;
} else
av_log(s, AV_LOG_DEBUG, “demuxer does not support additional id3 data, skipping\n”);
}
ff_id3v2_free_extra_meta(&id3v2_extra_meta);
if ((ret = avformat_queue_attached_pictures(s)) < 0)
goto fail;
if (!(s->flags&AVFMT_FLAG_PRIV_OPT) && s->pb && !s->internal->data_offset)
s->internal->data_offset = avio_tell(s->pb);
s->internal->raw_packet_buffer_remaining_size = RAW_PACKET_BUFFER_SIZE;
update_stream_avctx(s);
for (i = 0; i < s->nb_streams; i++)
s->streams[i]->internal->orig_codec_id = s->streams[i]->codecpar->codec_id;
if (options) {
av_dict_free(options);
*options = tmp;
}
*ps = s;
return 0;
fail:
ff_id3v2_free_extra_meta(&id3v2_extra_meta);
av_dict_free(&tmp);
if (s->pb && !(s->flags & AVFMT_FLAG_CUSTOM_IO))
avio_closep(&s->pb);
avformat_free_context(s);
*ps = NULL;
return ret;
}
