[FFmpeg-devel] [PATCH v2 1/5] libdc1394: Enable listing sources

[Marton Balint]

On Thu, 15 Oct 2020, Forest Crossman wrote:

> IIDC camera sources can now be listed by using the following command:
>
>    ffmpeg -sources libdc1394
>
> The basic structure of this function was borrowed from
> libavdevice/alsa.c:ff_alsa_get_device_list.
>
> Signed-off-by: Forest Crossman <cyrozap at gmail.com>
> ---
> libavdevice/libdc1394.c | 73 +++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 73 insertions(+)
>
> diff --git a/libavdevice/libdc1394.c b/libavdevice/libdc1394.c
> index 003335fdd8..ec74cea87a 100644
> --- a/libavdevice/libdc1394.c
> +++ b/libavdevice/libdc1394.c
> @@ -22,6 +22,8 @@
> 
> #include <dc1394/dc1394.h>
> 
> +#include "avdevice.h"
> +
> #include "libavutil/imgutils.h"
> #include "libavutil/internal.h"
> #include "libavutil/log.h"
> @@ -288,6 +290,76 @@ static int dc1394_close(AVFormatContext * context)
>     return 0;
> }
> 
> +static int dc1394_get_device_list(AVFormatContext *c, AVDeviceInfoList *device_list)
> +{
> +    int ret = 0;
> +    uint32_t i;
> +    dc1394_t *d;
> +    dc1394camera_t *camera;
> +    dc1394camera_list_t *list;
> +    AVDeviceInfo *new_device = NULL;
> +
> +    d = dc1394_new();

Can't this return NULL on failure?

> +    if (dc1394_camera_enumerate(d, &list) != DC1394_SUCCESS || !list) {
> +        av_log(c, AV_LOG_ERROR, "Unable to look for an IIDC camera.\n");
> +        ret = -1;

AVERROR_EXTERNAL

> +        goto out;
> +    }
> +
> +    device_list->nb_devices = 0;
> +    device_list->default_device = -1;
> +
> +    if (list->num > 0) {
> +        device_list->default_device = 0;
> +    }

You can omit the braces.

> +
> +    for (i = 0; i < list->num; i++) {
> +        new_device = av_mallocz(sizeof(AVDeviceInfo));
> +        if (!new_device) {
> +            ret = AVERROR(ENOMEM);
> +            break;
> +        }
> +
> +        camera = dc1394_camera_new_unit(d, list->ids[i].guid, list->ids[i].unit);
> +        if (!camera) {
> +            av_log(c, AV_LOG_ERROR, "Unable to open camera 0x%016"PRIx64":%"PRIu16"\n",
> +                   list->ids[i].guid, list->ids[i].unit);
> +            ret = -1;

Does it makes sense to continue the loop on this failure? If not, then use 
AVERROR_EXTERNAL error code.

> +            break;
> +        }
> +
> +        new_device->device_name = av_asprintf("0x%016"PRIx64":%"PRIu16,
> +                                              list->ids[i].guid, list->ids[i].unit);
> +        new_device->device_description = av_asprintf("%s %s",
> +                                                     camera->vendor, camera->model);
> +        dc1394_camera_free(camera);
> +
> +        if (!new_device->device_description || !new_device->device_name) {
> +            ret = AVERROR(ENOMEM);
> +            break;
> +        }
> +
> +        if ((ret = av_dynarray_add_nofree(&device_list->devices,
> +                                          &device_list->nb_devices, new_device)) < 0) {
> +            break;
> +        }
> +
> +        new_device = NULL;
> +    }
> +    if (new_device) {
> +        av_free(new_device->device_description);
> +        av_free(new_device->device_name);

This can potentially free an already allocated device name/description if 
the allocation of new_device for the next item fails. Alsa.c uses local 
variables to avoid this issue...

Regards,
Marton

> +        av_free(new_device);
> +    }
> +
> +    /* Freeing list of cameras */
> +    dc1394_camera_free_list(list);
> +
> +out:
> +    dc1394_free(d);
> +    return ret;
> +}
> +
> AVInputFormat ff_libdc1394_demuxer = {
>     .name           = "libdc1394",
>     .long_name      = NULL_IF_CONFIG_SMALL("dc1394 v.2 A/V grab"),
> @@ -295,6 +367,7 @@ AVInputFormat ff_libdc1394_demuxer = {
>     .read_header    = dc1394_read_header,
>     .read_packet    = dc1394_read_packet,
>     .read_close     = dc1394_close,
> +    .get_device_list = dc1394_get_device_list,
>     .flags          = AVFMT_NOFILE,
>     .priv_class     = &libdc1394_class,
> };
> -- 
> 2.20.1
>
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