[FFmpeg-devel] [PATCH v4 19/22] avformat: add avformat_alloc_input_context()
Diederick Niehorster
dcnieho at gmail.com
Fri Mar 25 16:10:38 EET 2022
avformat_alloc_input_context function analogous to
avformat_alloc_output_context2, except that it does not take a filename
argument as guessing the format by just the filename does not make sense.
avformat_alloc_input_context can be used e.g. with the avdevice
capabilities API, which needs an allocated input format with priv_data
(and default options) set, but device should not be opened.
Added some checks to avformat_open_input, for the case that a
AVFormatContext* allocated by avformat_alloc_input_context is provided:
1. if avformat_open_input's AVInputFormat *fmt argument is not NULL,
clean up any already set s->iformat
2. if s->url is already set and avformat_open_input's filename argument
is not NULL, free current url and replace by provided filename
3. if s->url is already set and avformat_open_input's filename argument
is NULL, do not set s->url to "", but keep current url
4. if s->priv_data has already been allocated, do not do so again.
4b. do reset options to default and apply provided options (if any)
5. add 4b to docs of avformat_open_input
Bump libavformat version.
Signed-off-by: Diederick Niehorster <dcnieho at gmail.com>
---
libavformat/avformat.h | 29 +++++++++++++++--
libavformat/demux.c | 74 ++++++++++++++++++++++++++++++++++++++----
libavformat/version.h | 2 +-
3 files changed, 95 insertions(+), 10 deletions(-)
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 027a914e13..004d81640f 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -2024,6 +2024,26 @@ AVProgram *av_new_program(AVFormatContext *s, int id);
* @}
*/
+ /**
+ * Allocate an AVFormatContext for an input format.
+ * avformat_free_context() can be used to free the context and
+ * everything allocated by the framework within it. NB: in general
+ * the correct format cannot be known (unless the user has extra
+ * information) until the file is opened. If forcing a format by
+ * this method, but it turns out not to match the file's format
+ * upon avformat_open_input(), the latter will throw an error.
+ *
+ * @param *ctx is set to the created format context, or to NULL in
+ * case of failure
+ * @param iformat format to use for allocating the context, if NULL
+ * format_name is used instead
+ * @param format_name the name of input format to use for allocating the
+ * context
+ * @return >= 0 in case of success, a negative AVERROR code in case of
+ * failure
+ */
+int avformat_alloc_input_context(AVFormatContext **ctx, const AVInputFormat *iformat,
+ const char *format_name);
/**
* Allocate an AVFormatContext for an output format.
@@ -2119,9 +2139,9 @@ int av_probe_input_buffer(AVIOContext *pb, const AVInputFormat **fmt,
* 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.
+ * @param ps Pointer to user-supplied AVFormatContext (allocated by avformat_alloc_context, or
+ * avformat_alloc_input_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.
@@ -2129,6 +2149,9 @@ int av_probe_input_buffer(AVIOContext *pb, const AVInputFormat **fmt,
* @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.
+ * Note that if a AVFormatContext allocated by avformat_alloc_input_context
+ * is provided, any demuxer-private options will be overwritten by their defaults
+ * before applying this new set of demuxer-private options, if any.
*
* @return 0 on success, a negative AVERROR on failure.
*
diff --git a/libavformat/demux.c b/libavformat/demux.c
index c1c9422ac0..b314477e47 100644
--- a/libavformat/demux.c
+++ b/libavformat/demux.c
@@ -217,6 +217,56 @@ FF_ENABLE_DEPRECATION_WARNINGS
return 0;
}
+
+int avformat_alloc_input_context(AVFormatContext** avctx, const AVInputFormat* iformat,
+ const char* format)
+{
+ AVFormatContext* s = avformat_alloc_context();
+ int ret = 0;
+
+ *avctx = NULL;
+ if (!s)
+ goto nomem;
+
+ if (!iformat) {
+ if (format) {
+ iformat = av_find_input_format(format);
+ if (!iformat) {
+ av_log(s, AV_LOG_ERROR, "Requested input format '%s' not found\n", format);
+ ret = AVERROR(EINVAL);
+ goto error;
+ }
+ }
+ else {
+ av_log(s, AV_LOG_ERROR, "You should provide an input format or the name of an input format when calling this function\n");
+ ret = AVERROR(EINVAL);
+ goto error;
+ }
+ }
+
+ s->iformat = iformat;
+ if (s->iformat->priv_data_size > 0) {
+ s->priv_data = av_mallocz(s->iformat->priv_data_size);
+ if (!s->priv_data)
+ goto nomem;
+ if (s->iformat->priv_class) {
+ *(const AVClass**)s->priv_data = s->iformat->priv_class;
+ av_opt_set_defaults(s->priv_data);
+ }
+ }
+ else
+ s->priv_data = NULL;
+
+ *avctx = s;
+ return 0;
+nomem:
+ av_log(s, AV_LOG_ERROR, "Out of memory\n");
+ ret = AVERROR(ENOMEM);
+error:
+ avformat_free_context(s);
+ return ret;
+}
+
int avformat_open_input(AVFormatContext **ps, const char *filename,
const AVInputFormat *fmt, AVDictionary **options)
{
@@ -233,8 +283,14 @@ int avformat_open_input(AVFormatContext **ps, const char *filename,
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)
+ if (fmt) {
+ if (s->iformat) {
+ if (s->iformat->priv_class && s->priv_data)
+ av_opt_free(s->priv_data);
+ av_freep(&s->priv_data);
+ }
s->iformat = fmt;
+ }
if (options)
av_dict_copy(&tmp, *options, 0);
@@ -245,7 +301,9 @@ int avformat_open_input(AVFormatContext **ps, const char *filename,
if ((ret = av_opt_set_dict(s, &tmp)) < 0)
goto fail;
- if (!(s->url = av_strdup(filename ? filename : ""))) {
+ if (filename && s->url)
+ av_freep(&s->url);
+ if (!s->url && !(s->url = av_strdup(filename ? filename : ""))) {
ret = AVERROR(ENOMEM);
goto fail;
}
@@ -288,12 +346,16 @@ int avformat_open_input(AVFormatContext **ps, const char *filename,
s->duration = s->start_time = AV_NOPTS_VALUE;
- /* Allocate private data. */
+ /* Allocate private data and set options. */
if (s->iformat->priv_data_size > 0) {
- if (!(s->priv_data = av_mallocz(s->iformat->priv_data_size))) {
- ret = AVERROR(ENOMEM);
- goto fail;
+ /* allocate if not already allocated */
+ if (!s->priv_data) {
+ if (!(s->priv_data = av_mallocz(s->iformat->priv_data_size))) {
+ ret = AVERROR(ENOMEM);
+ goto fail;
+ }
}
+ /* Overwrite any options already set (1: back to defaults, 2: apply options, if any) */
if (s->iformat->priv_class) {
*(const AVClass **) s->priv_data = s->iformat->priv_class;
av_opt_set_defaults(s->priv_data);
diff --git a/libavformat/version.h b/libavformat/version.h
index 1ab39022c2..7cd09f7ef8 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -32,7 +32,7 @@
#include "version_major.h"
-#define LIBAVFORMAT_VERSION_MINOR 23
+#define LIBAVFORMAT_VERSION_MINOR 24
#define LIBAVFORMAT_VERSION_MICRO 100
#define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
--
2.28.0.windows.1
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