diff mbox series

[FFmpeg-devel,31/35] avformat: add avformat_alloc_input_context()

Message ID 20210607230414.612-32-dcnieho@gmail.com
State Superseded, archived
Headers show
Series avdevice (mostly dshow) enhancements
Related show

Checks

Context Check Description
andriy/x86_make fail Make failed
andriy/PPC64_make warning Make failed

Commit Message

Diederick C. Niehorster June 7, 2021, 11:04 p.m. UTC
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 that 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.

Signed-off-by: Diederick Niehorster <dcnieho@gmail.com>
---
 libavformat/avformat.h | 20 +++++++++++++
 libavformat/utils.c    | 66 +++++++++++++++++++++++++++++++++++++++---
 libavformat/version.h  |  2 +-
 3 files changed, 83 insertions(+), 5 deletions(-)
diff mbox series

Patch

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 5e1e82a315..b444602b86 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1896,6 +1896,26 @@  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.
diff --git a/libavformat/utils.c b/libavformat/utils.c
index fe8eaa6cb3..2e8084a41b 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -478,6 +478,56 @@  static int update_stream_avctx(AVFormatContext *s)
 }
 
 
+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)
 {
@@ -492,8 +542,14 @@  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);
@@ -504,7 +560,9 @@  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;
     }
@@ -547,8 +605,8 @@  int avformat_open_input(AVFormatContext **ps, const char *filename,
 
     s->duration = s->start_time = AV_NOPTS_VALUE;
 
-    /* Allocate private data. */
-    if (s->iformat->priv_data_size > 0) {
+    /* Allocate private data if not already allocated. */
+    if (s->iformat->priv_data_size > 0 && !s->priv_data) {
         if (!(s->priv_data = av_mallocz(s->iformat->priv_data_size))) {
             ret = AVERROR(ENOMEM);
             goto fail;
diff --git a/libavformat/version.h b/libavformat/version.h
index 13df244d97..d5dd22059b 100644
--- a/libavformat/version.h
+++ b/libavformat/version.h
@@ -32,7 +32,7 @@ 
 // Major bumping may affect Ticket5467, 5421, 5451(compatibility with Chromium)
 // Also please add any ticket numbers that you believe might be affected here
 #define LIBAVFORMAT_VERSION_MAJOR  59
-#define LIBAVFORMAT_VERSION_MINOR   5
+#define LIBAVFORMAT_VERSION_MINOR   6
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \